Archaeoastronomy, Celts

Adriano Gaspani: Astronomy of the ancient Celtic culture

Welcome and thank you for visiting this section of the Archaeoastronomy portal on Historia Vivens Web. Adriano Gaspani's articles, the result of years-long studies and researches, accompany us in the world of the sky observations during the Iron Age in Europe. There is a civilization, or better to say a group of tribes, whose culture has decisively influenced the development of all the other European cultures, and whose astronomical and mathematical skills and knowledge have proved to be quite sophisticated although emerging only recently: these are the Celts!

Image: Adriano Gaspani visiting the historical camp at a Celtic Reenactment event in Italy.

The Author invesitgates archaeological finds and sites with astronomical significance, as well as the myths and the period accounts which have come down to us over centuries. The outcome is a comprehensive and fascinating picture of the importance that stars, astronomy and astrology played for the ancient Celts. Some outstanding contributions made by Adriano Gaspani to the research in this field include the first correct interpretation of the only existing Celtic lunar-solar calendar, the Coligny bronze plate, on which the Author held a lecture at the Haute Ecole d’Etudes Celtiques at the Sorbonne University in Paris (France), and the archaeoastronomical study of the Golasecca Culture settlements, which flourished in subalpine Italy from the 13th to the 4th century BC.

Here below you can find Adriano Gaspani's contributions (mostly in Italian language) published on Historia Vivens Web. Texts and images, unless otherwise attributed, are provided by the Author himself, and are his copyright. Please note that, to ease the reading, all articles, in full version and accompanied by pictures and notes, are free to download in PDF format. We hope you will enjoy the contents and wish you a pleasant surfing. This section is constantly evolving, please come back often for the latest updates. Thank you!

The Celts and History...

The Celts in the Iron Age occupied much of the territory of Central Europe, from where they gradually moved west through Germany into France, and then expanded to the south, in northern Spain, as well as to the far north, in the territories of Scotland, Wales and Ireland. The 4th century BC marked the beginning of the great expansions of the transalpine Celts, who descended into Italy and conquered Rome in 387/386 BC. By the 3rd century BC, the Celts stretched from Ireland to Hungary, with isolated tribes from Portugal to Turkey. Since then all the written testimonies by Latin and Greek authors started including information about the Celts, who, as Roman historian Titus Livius (69/54 BC-17 AD) wrote, “were a strange and unknown race” (Ab Urbe Condita, 5, 17)...

Image: expansion of the Celtic cultures in the 3rd century BC according to Francisco Villar in “Los Indoeuropeos y los origenes de Europa” (Italian edition). Released into the public domain, source: Wikimedia Commons.


The Celts and Astronomy...

The Celts practiced Astronomy at a high level both for speculative and for practical purposes, as witnessed by the calendric finds that show an excellent knowledge of the apparent motion of the Moon and of the Sun. The astronomical knowledge of the Celts was to a large degree inherited from preceding cultures that built the megalithic monuments. It is highly probable that an appreciable influence was also exercised by the Greeks philosophy and cosmogony, in particular the Pythagorean one, as confirmed by several ancient Greek documents attesting an intense exchange of ideas and experiences among the Pythagoreans of the Syracuse school and the Celtic Druids who came in contact with them in the various flourishing Greek colonies along the southern coast of France. Nevertheless, it's also true that a number of independent discoveries were also made by the Celts themselves...

Image: Stonehenge megalithic site at sunset. Copyright: Simon Wakefield. Source: Wikimedia Commons.

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The Druids and Astronomy...

The Celtic society compared with other ancient civilizations was characterized by an astonishing number of people devoted to the mastering and teaching of the "Natural Philosophy" (i.e. the study of nature and the physical universe before the advent of modern science, somehow the precursor of today natural sciences). Despite the trend to identify all them together under the general term Druid, in reality there were three different groups of learned people with distinct responsibilities: the Bards, singers or poets, who were the keepers of the oral history of the Celtic people, the Vates or Filid, seers and soothsayers, diviners of omens and portents, who were responsible for rituals and sacrificess, and finally the Druids, a privileged and highly venerated religious caste that held a position of great importance and respect within the Celtic communities as keepers of all knowledge, including mathematics and astronomy, natural and political science, law and religion, history and tradition of the Celtic life. Greek historian, geographer and philosopher Strabo (64/63 BC – c.24 AD) wrote: "among all the Gallic peoples three sets of men are honoured above all others: the bards, the vates, and the druids. The bards are singers and poets, the vates overseers of sacred rites and philosophers of nature, and the Druids, besides being natural philosophers, practice moral philosophy as well..." ("Geography", 4.4.4).

Image: creative illustration of a Druid in his judicial habit from "The Costume of the Original Inhabitants of the British Islands", 1815, by S.R. Meyrick and C.H. Smith. Source: Wikimedia Commons.

The Druids, who could be either male or female, were teachers, philosophers, and lawyers. The science of the Druids, who passed down orally a great number of mnemonic rules to their scholars over 20 years of training, was composed mainly of a variety of empirical correlations, discovered and improved over centuries, between different natural phenomena. As reported by Julius Caesar: “they hold various lectures and discussions on astronomy, on the extent and geographical distribution of the globe, on the different branches of natural philosophy, and on many problems connected with religion” ("De Bello Gallico", VI, 13). Pomponius Mela (?-45 AD), Roman geographer adds: “And yet, they have both their own eloquence and their own teachers of wisdom, the Druids. These men claim to know the size and shape of the earth and of the universe, the movements of the sky and of the stars, and what the gods intend” (De Chorographia, 3, 2, 18). The Druids were also able to predict eclipses, as well as the tides as natural consequences of their knowledge of the lunar motion. Such ability to make predictions about the occurrence of the periodic astronomical phenomena, like the eclipses or the visibility of stars and planets, has surely strengthened the folk belief in the magic power of the Druids.

The astronomical knowledge of the Ancient Celts

From the great four seasonal festivals to the Zodiac of Grand, from the Coligny Calendar to the sacred nemetons, the text offers an interesting compendium of the astronomical and mathematical knowledge achieved directly by the Celts and partly also inherited from the previous cultures that built the megalithic monuments in Ireland, Wales, Brittany and throughout Europe. That of the Celts was in many respects a developed culture devoted to the study and interpretation of nature, the observation of the stars together with the monitoring of the Sun and the Moon movements...

Image: the Trundholm sun chariot, Denmark - source: National Museum Copenhagen.

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The Celts and the time measurement...

The ability to perceive the rhythms of nature and live in harmony with it has always represented an essential feature of any cultures in the pre- and proto-historic world that were devoted to farming, and therefore in need of a calendar, or at least a set of rules, that could help to effectively measure the time and divide the year, thus allowing a successful and in-time planning of the tilling and sowing the fields, as well as of any agricultural activities aimed to obtain a good harvest. This was also the case of the ancient Celts, whose economy was predominantly rural like many other cultures of the Iron Age. The Sun and the Moon with their cyclical motion were crucial, as the Moon allowed to split the time in weeks, fortnights and months, while the Sun helped to mark the year. The Celts adopted a division of the time the suited at the best possible to their agricultural and livestock needs, thus being always able to exploit the resources provided by the Nature, they lived in great armony with and knew very well. The Celts measured the time by nights followed by days, not the reverse as we do today, as they considered themselves children of the night, and believed the day arises from the night just like the life from the death. 

Image: modern depiction of a Celtic village. Credits: The Celts by Nachiii  on DeviantArt.

No written documents or scientific treatises were produced by the Celts, except for some calendric tables compiled much later mainly for ritual purposes, when the process of Romanization of the Celtic people was well advanced. Some fragments of these calendric tables were discovered during the last century. The best example was found at Coligny (France) in 1897...

The Coligny Calendar and time calculation

The Coligny lunisolar calendar is an engraved bronze tablet preserved in 73 fragments, originally 1.48 m wide by 0.9 m tall, dating from the turn of the 1st century BC. The calendar, which achieves a complex synchronization of the solar and lunar months, was discovered buried in a field near Coligny in the Ain region of France in 1897, and is now kept at the Gallo-Roman Museum in Lyon. The Coligny Calendar is a sophisticated lunisolar calendar based on cycles of five years, each consisting of 12 months plus 60 additional days to be intercalated according to certain rules to synchronize to each other the apparent motions of the Sun and the Moon. The five-year cycle was then part of a longer 30-years cycle called Saeculum by Roman historians.

Image: the re-assembled tablet of the Coligny Calendar - source: Wikimedia Commons

The astronomical knowledge encoded in it seems to be very sophisticated, at least limited to the apparent lunar and solar motions on the celestial sphere useful for genuine calendric purposes, but deeper analysises confirm that this find is only a limited, rather important, testimony of the existence of a refined astronomical knowledge in the Celtic culture. The calendar embodies a mathematical model that require an excellent, but empirical, knowledge of the geocentric theory of the Lunar motion as well as some very good empirical ideas on the laws regulating the apparent motion of the Sun in the sky. Obviously such knowledge is of a totally empirical nature and based very probably on the experimental search for some regularity among the apparent configurations of the visible celestial bodies. Each year is divided into two halves referred to the winter and the summer months. Each month is then divided into two half-months or "fortnights", the dark and the light. The days are measured from sunset to sunset in order to keep the division in two periods: again the dark and the light... 

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The Celts and the stellar astronomy...

Adriano Gaspani believes that the astronomical knowledge of the Celts was not limited only to the domain of the calendric practice, but it also encompassed the stellar astronomy, i.e. the observation of the stars, that could be efficiently practiced together with the monitoring of the Sun and the Moon. If the Celts were able to build the Calendar of Coligny, then they were also perfectly able to make stellar positional astronomy, although this was obviously limited to the data acquired by the naked eye observation and monitoring of the sky visible at that time. The Author proposes that stellar astronomy was of fundamental importance both for agricultural and for social purposes, as it provided an excellent method for fixing the dates both for the beginning and the end of the two seasonal periods of the agricultural life, Winter and Summer, as well as of the festivals, gatherings and other remarkable happenings within the Celtic communities. The use of the astronomical observation of the stars serves as high-precision tools for agricultural purposes. This is not possible if to rely solely on the apparent solar and lunar monitoring.

Image: a close-up of Sirius. Source: public domain. Credits: Akira Fujii - NASA Hubble European Space Agency.

Furthermore, stellar astronomy ruled also the times of the four great seasonal festivals of the Celtic culture by connecting the dates for their occurrence with the heliacal rising of certain stars. The heliacal rising of a star occurs annually when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period when it was not visible, hidden below the horizon. The use of the heliacal rising of the stars to determine the dates of the farming activities and needs was quite widespread among several ancient civilizations, such as Egyptian or Greek, as well witnessed by Hesiod’s poem the "Works and Days". Also the Celtic seasonal festivals were tailored to the heliacal rising of certain given stars: the Trinox Samoni festival would be celebrated at the new Moon immediately after the heliacal rising of the star Antares. The other festivals would be celebrated on the day of the heliacal rising of Capella, for the festival of Imbolc; on the day of the heliacal rising of Aldebaran, for the festival of Betaine, while Lugnasad was celebrated when Sirius rose with the Sun.

The Celtic seasonal festivals

The existence of four ritual festivals, celebrated every year by the Celts, is a well-known and accepted fact. These festivals marked the turning of the seasons and are: Trinox Samoni, Imbolc, Belteine and Lugnasad, all listed in chronological order, with the first marking also the beginning of the Celtic year. All festivals, except for Trinox Samoni, seems to be devoted to an individual deity, while the dates of their celebrations during the year appear to be related to some astronomical evidences. The Author assumes that the heliacal rising of a given star (or stars) would identify the days of a given festival...

Image: the wheel of the year and the four great Celtic festivals. Copyright & source: Tara Celebrations.

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The Celts and Astronomy: testimonies and case studies

The level of astronomical knowledge reached by the Celtic culture and their druids was reasonably high as it is attested by the above mentioned calendric finds that show an excellent knowledge of the apparent motion of the Moon and of the Sun. However there are several other findings and testimonies that can help us to shed light on the subject. Julius Caesar was among the first to mention the astronomical knowledge reached by the Celts, crediting the priestly class of the druids with a great knowledge of the sky, the stars and their motions, as well as the ability to describe and interpret the natural phenomena: “…they likewise discuss and impart to the youth many things respecting the stars and their motion, respecting the extent of the world and of our earth, respecting the nature of things, respecting the power and the majesty of the immortal gods.” ("De Bello Gallico", VI, 14).

Pliny the Elder reports the great importance of the Moon for the Celts, as the months, the days and the 30-year long cycle called Saeculum, always begin with the first qwuarte Moon phase.

Image: a Celtic druid as interpreted by the Ancient Celts reenactors of the Terra Taurina group from Italy (copyright and source: Historia Vivens Web).

According to Greek historian Diodorus Siculus (ca. 90- ca. 27 BC) the Druids and the Pythagoreans shared beliefs and views: “…for the opinion of Pythagoras prevails much amongst them, that men's souls are immortal, and that there is a transmigration of them into other bodies, and after a certain time they live again…” (Bibliotheca historica, book I). Surely the two schools were in many ways similar to each other: the women were also allowed, certain numbers were considered magical as well, and the knowledge was to be passed down orally. Theologian Hippolytus of Rome (170-235 AD) reports: “…and the Druids investigated to the very highest point the Pythagorean philosophy… the Celts esteem these as prophets and seers, on account of their foretelling to them certain (events), from calculations and numbers by the Pythagorean art…” (Refutatio Omnium Haeresium, book I, chapter 25).

Besides the classical authors, another source of information regarding the Celtic culture is represented by the oral traditions of the Irish, Welsh, Scottish and Breton cultures, that succeeded in preserving many customs as they managed to resist much longer than other colonies Celtic to the interference of the new emerging folks, when in the 1st century AD the slow decline of the Celts began, being forced to fight the Romans in the south, the Germans and the Angles in the north. A significant account comes from the Irish epic literature concerning the early adventures of Fionn mac Cumhaill, or Finn MacCool, a mythical hunter-warrior of Irish mythology and the future leader of the Fianna. Finn was brought up in secret in the forest of Sliabh Bladma by Druidesses Bodhmall and Liath Luachra who taught him the arts of war and hunting and introduced him as well to the sacred precepts - literally translated from the ancient Irish: "... then taught him the secrets of the Druidic arts: the virtues of herbs and plants, the habits of the animals in the forest and their sounds, the names and positions of the stars in the sky…".

Finally, the different case studies described here below represent only little evidence of the great importance of the sky observation for the Celts, and how deep was the astronomical knowledge in astronomy of their druids. The still ongoing studies let arise another image of the Celts: the image of wild barbarians is gradually dismantled and replaced with that of a refined culture devoted to the study, observation and interpretation of Nature.

Astronomy and the Celtic coinage

Among the several archaeological finds helping the researchers to deepen their knowledge of the high level of astronomy practiced by the ancient Celts a key role is surely played by the Celtic coins, which often depicted astronomical symbols and were minted in large quantities and with great frequency by the various Gallic tribes from the late 4th century BC to the late 1st century BC. also the ancient Greeks and Romans minted coins with depictions of astronomical objects, they were very few in number and only in limited cases, while the amount of Celtic coins with astronomical symbolism found during various excavations is comparatively quite high. The history of coinage among the Celtic tribes finds its roots in their economic and political links to the ancient Greece, in terms of trade and warfare, and in particular through southern Gaul, Macedonia and Thracia, and the Empire of Alexander the Great (356-323 BC) and his successors. The Celtic coinage was initially influenced by the Greek one, faithfully reproducing the Greek designs, especially the motifs of the Macedonian coins from the time of Philip II of Macedon (382-336 BC) and his son, Alexander the Great. And in fact Greek subjects and even letters can be especially found on various Celtic coins from southern France. Anyway, later soon the Celts started to modify the foreign design to match their own taste, culture and worldview. So, as time went by, the images imprinted on the coins gradually evolved becoming more original to include Celtic motifs and subjects, such as heads and skulls, horses and warriors, gods and goddesses, chariot wheels and spirals, thunderbolts and lightning, as well as a variety of other animals and mythical creatures, the sun, the moon and several other astronomical symbols, with a growing trend towards abstraction.

Image: a Celtic reenactor of the "Boiové a Fergunna" group casting coins during a living history display in Italy. Copyright and source: Historia Vivens Web.

The sky on the Celtic coins

The Celtic coinage is characterized by a rich and meaningful astronomical symbolism, which is the result of a constant and careful observation of the sky and the celestial phenomena. The representations of the sky on the Celtic coins either consists of a simple symbolic transposition of the celestial objects, or corresponds to specific and highly spectacular astronomical phenomena that were observed in the sky by the Celtic druids. It is usually possible to identify such phenomena by referring to the astronomical literature in the Far-Eastern annals, mainly the Chinese, Indian, Korean and Japanese ones. While in case of recurring phenomena, such as the passage of comets with elliptical orbits, the astronomical calculations helps to identify and reconstruct the trajectory in the sky as it was observed by the Celtic people settled in Europe during the Iron age…

Image: detail of the hoard of about 70,000 Celtic silver alloy coins found in a field in Jersey (Channel Islands) in 2012, the world's largest of its kind. Copyright & source: Jersey Heritage.

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Solar eclipses and the Unelli's coin

An outstanding example of the astronomical depictions on Celtic coins is provided by a coin minted by the Unelli tribe, one of the Armoric states of Gallia, settled in the Cotentin Peninsula (also known as the Cherbourg Peninsula) in Normandy region of today France. Currently only one copy is known. On the noble side of the coin, the observe, a male head is depicted, while the reverse shows the image of a huge wolf appearing to devour or spit the sun with the head turned back on itself, the muzzle wide-open, both jaws touching the solar disc which bears an internal cruciform motif and the crescent moon next to it. From the rear-end of the wolf a leafy branch emerges, while beneath its belly an eagle with unfolded wings is depicted poised on a snake. Above the wolf is the trace of a sloping palm and on the right unexplained emboss occur.

Image: the coin minted by the Unelli tribe during the 1st century B.C. and its relief.

The image has been interpreted in several ways: the wolf devouring the moon and the sun and then regurgitating the vegetation may be that of rampant wilderness in which the very order of the universe is threatened or expressing the end and the rebirth or also restoring the life to the universe. But the interpretation becomes very suggestive if we assume that the crescent depicted on the coin is not the moon, but just the image of the crescent-sun that remains visible during a partial solar eclipse when three quarters of the sun are blocked by the moon. Then the coin of the Unelli could simply recall a solar eclipse observed in Northern Gaul in the first century BC. The calendar of Coligny clearly suggests that the Druids were aware of the apparent motion of the Moon in the sky as well as of its characteristic periodicities. The ability to predict eclipses is a natural consequence of this knowledge…

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The Armorican coins and the Comete

Among the coin hoard found in archaeological excavations all over Europe are to especially considered the complete series of Armorican coins, that have been minted by the Celtic people settled in Armorica, an ancient region geographically correspondent to today's Brittaby in northern France, and in particular the extremely interesting coins minted by the Celtic tribe of the Curiosolitae, often bearing the representation of stellar objects, including the depiction of a comete seen above the horizon, most likely the Halley comet during its passage in year 87 BC since the coins date to a time period between 100 and 60 BC.

Image: a Celtic stater found in Armorica region (copyright & source: Numis Antica via Wikimedia Commons).

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The Celtic Carnix

One of the features common to all the Celtic tribes is the use of the Carnyx, the long and heavy ritual bronze horn ending in a dragon's head, wolf or wild boar, typical of the Iron Age Celts, and widely spread between c. 200 BC and c. AD 200. It was a type of bronze trumpet with an elongated "S" shape. The word “carnyx” is derived from the Gaulish root, "carn-" or "cern-" meaning "antler" or "horn," and the same root of the name of the god, Cernunnos. This particular type of wind instrument has been found in several samples during the archaeological excavations and is represented on many findings, including reliefs, such as the famous Gundestrup cauldron, a richly decorated large silver bowl found in Denmark form the late La Tène period or early Roman Iron Age, the Trajan's Column, a 2nd century AD triumphal column commemorating Roman emperor Trajan's victory in the Dacian Wars, and even on Roman coins.

Image: replica of a carnyx on show at a living history display in Italy (copyright & source: Historia Vivens Web).

Several ancient historians and authors testified of the terror effect among the Roman legionnaires caused by the hoarse and strong sound of dozens of such horns played in battle.

Greek historian Diodorus Siculus (ca. 90 - ca. 27 BC) wrote: "their trumpets again are of a peculiar barbarian kind; they blow into them and produce a harsh sound which suits the tumult of war" (Histories, 5.30), while his fellow countryman Polybius (ca. 200 - ca. 118 BC) reported: “…the Romans were terrified by the fine order of the Celtic host and the dreadful din, for there were innumerable horn-blowers and trumpeters, and, as the whole army were shouting their war-cries at the same time, there was such a tumult of sound that it seemed that not only the trumpets and the soldiers but all the country round had got a voice and caught up the cry” (Histories II, 28-30).

The study of both archaeological finds and historical records has confirmed that this instrument was not played only in battle to unnerve and terrify the enemies, but it was also played at feasts, weddings, funerals and festivals, and especially used during the Druidic rites in the forests, as well as on occasion of the celebrations that took place on occasion of solar and lunar eclipses or comets' passages. Therefore, it was possible to highlight the existence of an astronomical symbolism related to the particular shape of the carnyx, as well as to its use arising from the transposition of the Indo-European cosmological conception in the Celtic druidic culture.

Here below the recording of a reconstruction of the Deskford carnyx, the head of an Iron Age trumpet found in the north-east of Scotland around 1816 and dating from 80-250 AD:

Celtic Astronomy: the evidence of the sacred places...

A further evidence of the deep astronomical knowledge achieved by the ancient Celts is represented by the so-called Nemeta (plural of the word Nemeton), which refers to a wide category of sacred and ritual open spaces of the ancient Celtic religion, such as shrines, groves, temples, necropolis and burial mounds, where the Iron Age Celts held their religious festivals, celebrated their rituals, including sacrifices, and buried people. The Nemeta were usually situated in natural areas and consisted of a clearing in the woods, a votive tree trunk or shaft or water spring, like a well or any water sources, a wooden or stony temple structure (usually inherited by previous civilizations as it is the case of the megalithic monuments in the North Atlantic Europe, like Stonehenge in England) and other natural features. Several Celtic shrines were surrounded with an earthwork, a palisade, a bank, or a ditch, usually circular or oval in plan but sometimes also squared or rectangular. The classical authors often identified the ritual sites of the Celts in mainland Europe with sacred groves of trees, as the druids, according to the Roman writers Pliny, Lucan, and Julius Caesar, did not meet in stone temples, or similar permanent structures, but in the woods, especially of oak forests, as the oak was considered the most sacred tree.

Image: copyright Historia Vivens Web.

The Celtic word "Nem" means the celestial vault. And, in fact, the Nemeta can be rightly considered as well-working astronomical observatories. The analysis of the structure of the Nemeta built by the Celts during the Iron Age shows that astronomy played a key role both in the choice of the sites where they were built, as well as in their orientation with respect to the significant astronomical directions, and finally also in defining their construction structure. The reorganization on the ground of these sacred places highlights how the directions, the arrangement of the poles, and also the position of the bodies inside the burial mounds, are based on specific astronomical schemes.

The Nemeton of Libenice and the Akropolis of Zavist

Astronomy played a decisive role in the identification and implementation of the so-called Celtic Nemeta. Two emblematic samples, which have undergone a archaeoastronomical survey, are to be found in Bohemia, Czech Republic, a few kilometers from Prague: the Nemeton of Libenice and the Acropolis of Závist, both dating back to 500 BC about. The Nemeton of Libenice was built and used by the Boi Celtic tribe and later abandoned around 400 BC when they left the area to settle in Italy. The sanctuary was a rectangular enclosure of about 24m x 80m surrounded by a moat.

Image: aerial view of the Acropolis of Zavist. Source: Celtic Europe, 

Another site with Archaeoastronomy significance is the Acropolis of Závist, or more specifically its triangular tower. The Acropolis is located within a fortified site on a hilltop (elevation 391m), a Celtic oppidum, dating back to the VI-V century BC.

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The "Viereckschanzen" or sacred enclosures...

Several Celtic shrines had the form of a squared or rectangular space enclosed by a bank, a ditch or also a palisade. The German term Viereckschanze (plural Viereckschanzen, meaning "four-corner-rampart") identifies the quadrangular sacred enclosures built by the Celts during the Iron Age in many areas of Central and Western Europe. Sometimes the sacred enclosures of the Celts contained a man-made structure, usually they were placed in liminal zones, such as muddy areas between land and water or at the boundaries between territories.

Image: reconstruction of the features of a typical Viereckschanze (copyright Wieland 1999, Zeichnung J. Sailer, source:

Although the Viereckschanzen are widespread in Germany, northern France and also in the Iberian Peninsula, their function is not yet completely understood by the scientists: for decades these sacred enclosures were believed to be Celtic temples or sanctuaries, but recent excavations and studies suggest a wider interpretation of the Viereckschanzen, as bearing multiple social, political, and religious functions. Nevertheless, a significant astronomical orientation of the Viereckschanzen has been definitely proved as also Adriano Gaspani confirms in this article reporting us about the results of his own archaeoastronomical study and survey. The analysis performed using artificial neural networks and fuzzy logic has allowed to define the orientation criteria which were common to the majority of the "Viereckschanzen", thus highlighting the remarkable similarity of the construction criteria adopted by the different Celtic tribes settled in mainland Europe during the second half of the Iron Age...

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Celtic Astronomy: the evidence of the Oppida

A clear relationship with astronomy is witnessed not only by the sacred sites, but also by certain Oppida especially those hosting the most advanced druidic classes. The Latin word Oppidum (plural oppida) was first used by Caesar to describe the Celtic fortified settlements he discovered during his Gaul campaign. In archaeology, the term is now used to describe a large fortified Iron Age settlement built on fresh sites, usually on an elevated position, covering a minimum area of 15ha and dating back to the second half of the 2nd and 1st centuries BC (the late La Tène period), and completely surrounded by fortifications, both natural (rivers, cliffs, and swamps) and constructed (walls of earth and stone) topped by a wooden palisade.

Image: reconstruction of a Celtic oppidum from the La Tene period. Source:

The oppida, often located on trade routes or natural resources (especially iron mines), were important economic and political centres playing a key role in displaying the power and wealth of the local communities. They are considered to be the first towns to the north of the Alps.. Some oppida, like Bibracte in France, Manching in Germany, and Stradonice in Czech Republic, were densely populated and centres of industrial production, and also the seat of remarkably advanced druidic schools.

The monumental basins of the ancient Celts

Water especially was held as sacred and worshiped by the ancient Celts. Whether or not they were enclosed in a ritual site, water sources and springs were believed to possess healing powers and also to be entrances to the Otherworld. The Celtic oppida often hosted ritual fountains that were equipped with highly efficient water supply systems and have been classified by the archaeologists as "monumental basins" with regards both to the quality and quantity of the stone materials used, as well as to their huge dimensions. Traces of such buildings have been found in several oppida, such as Argentomagus, Glanum, Marseille, Lugdunum and Bibracte.

Image: the monumental basin of Bibracte during the excavations in 1988. Copyright and source: Havang.(nl) - Wikimedia Commons.

The shape of these ritual fountains is generally square or rectangular, as in the case of Marseille, Lyon, Bourges and Vaison, but there are also samples of semi-circular basins like at Glanum, or also circular, hexagonal or even octagonal like the ones in Metz, Lons-le-Gaunier and Saint-Maur. While in Bibracte the basin had an elliptical shape. The monumental fountains played the practical function of water collectors, but had also a ritual significance given that the Celts revered the waters attributing high divine characteristics to the water-springs and througout Europe they approached springs and lakes as sanctuaries and places of healing. The design and supervision of the construction works of the monumental fountains were carried out by the Druids. So it is conceivable that both the choice of the site as well as the shape and the orientation of such fountains were based on some certain astronomical, mathematical and ritual criteria. This is confirmed also by the survey of the fountain in Bibracte, which has a transversal orientation corresponding to the rising sun during the Winter Solstice and to the setting sun during the Summer Solstice, thus confirming how the druids of the Aedui tribe were aware of the Pythagorean geometry and had the mathematical knwoledge needed for the calculations...

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The Celtic burial mound at Eberdingen-Hochdorf

In the late 1970s a Celtic circular burial mound of earth and stones from the last Hallstatt period, dating from the 6th century BC, was discovered under a barrow near the village of Hochdorf, not far from Stuttgart, in Southern Germany. Under the mound a richly-furnished burial chamber was brought to light with the remains of a roughly 40 years old Celtic aristocrat man from the time of the Celtic "Princes Age", when Central Europe was under the rule of noble warriors, who lived in small fortified settlements located on hilltops and surrounded by stone walls and clay trenches.

Image: the reconstructed burial mound at Hochdorf (copyright and source:

Careful excavations and yearlong researches allowed the burial chamber with its magnificent furnishings to be reconstructed in every detail and revealed that astronomical criteria are behind its building. The planimetrical analysis of the tomb and the burial chamber reveals that the planning has been influenced by the studying of Astronomy and in particular by observing the rising and the setting of the Moon together with the visibility of the Orion constellation in the VI century B.C. In 1998 Adriano Gaspani published the conclusions he drew from calculations concerning the Celtic burial mound: the shape and the orientation of the burial chamber were such that its diagonals pointed in the directions of the extreme rising and setting points of the moon during its 18.6 yr. cycle. Besides, the position of the body of the Prince was orientated along the local meridian...

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