Celtic hill forts and fortified towns, used by Iron Age tribes as defense points against invading Roman armies, were superseded by unfortified religious and commercial centers known as oppida.

By the beginning of the second century b.c.e., the Celtic expansion, which encompassed lands from Asia Minor to the British Isles, was waning. In Austria, southern Germany, and western Hungary, the fierce and warlike Celts, who spoke Indo-European languages later classified as Celtic, were beginning to feel the force of Rome. By the middle of the first century b.c.e., when the Roman legions marched into western Europe, many of the old Celtic hill forts had been replaced by newly established fortified towns. These towns, referred to by the invading Romans as oppida, had grown into large commercial centers as a result of lucrative trading. Caesar, Julius
Vercingetorix

The Celts—loosely related congeries of tribes whose collective label derives from their Greek name, Keltoi—traditionally built fortified hilltop settlements that were defended by multiple earthwork ramparts, wooden palisades, and ditches. Prehistoric people used antlers to dig the soil and willow baskets to remove it. Two hundred people could dig a ditch and erect a 13-foot-high (4-meter-high) bank topped with one thousand stakes in a matter of one hundred days. By the time of Rome’s advancement, scores of Celtic hill forts were scattered throughout western Europe and were used as defenses against the Roman armies. In his Comentarii de bello Gallico (51-52 b.c.e.; Commentaries, 1609), Julius Caesar listed oppida belonging to twenty-nine different Gallic tribes and regarded each oppidum as a commercial center.

Some hill forts were permanently inhabited during the Iron Age and others were occupied only during times of crisis. The oldest date from 1500 b.c.e. Originally constructed as refuges, storage sites, or as domiciles for kings, many of these forts could be entered only through a series of mazes. They enclosed villages or towns of circular huts and could house permanently up to one thousand people, as well as large numbers of refugees during times of crisis. According to Caesar, the oppidum of Avaricum (modern-day Bourges, France) sheltered forty thousand individuals during one Roman siege. The fully enclosed weatherproofed huts measured about 36 feet (11 meters) in diameter, were roofed with thatch made of reeds, and walled with vertical wooden planks. Many large grain storage pits as deep as 10 feet (3 meters) were also dug within the forts, ensuring survival during long Roman sieges.

A 1955 excavation in Bavaria, Germany, revealed that the oppidum of Manching housed between one thousand and two thousand people. In southern Germany, another site known as Heuneburg Towers, which was excavated in 1876, revealed a Celtic stronghold dating back to 1500 b.c.e. By examining the layers of debris left by successive generations, scientists were able to determine that this particular hill fort had been demolished and rebuilt more than twenty times. The central building of each enclosure served as a religious shrine.

By 600 b.c.e., an era referred to by archaeologists as the Hallstatt period and named after the Austrian village where its remains were first identified, the use of ironworking technology had advanced to the point that the Celts had spread their culture and hill forts across a geographic area that covered Italy to Ireland and Spain to the Ukraine. By the fifth century b.c.e., partly as a result of trade disruptions, many of the early Hallstatt hill forts were abandoned, and the wealth of the early Celts began to fade.

By 450 b.c.e., however, the second Iron Age period of Celtic culture, known as the La Tène period, had emerged and the earlier hill fort sites were refurbished and restored.

Named after a key archaeological site on the east side of Lake Neuchâtel in Switzerland, the La Tène period was characterized by iron swords and household utensils decorated with distinctive curvilinear patterns that express the vigorous and exuberant Celtic art style. The La Tène period lasted from the mid-fifth century b.c.e. until the Roman conquest and spread across France, Germany, Austria, Switzerland, Britain, Ireland, Bohemia, parts of Iberia, and Italy.

Before 400 b.c.e., the Celtic hill forts had used natural topographic features such as cliffs for defense. After that time, the La Tène Celts constructed contour forts, in which an entire hilltop, encircled by banks and ditches, made enemy assault almost impossible. The best-known British hill forts from this period, built by a Celtic tribe known as the Western Belgae, are Hod Hill (later turned into a military establishment by the Romans), Hambledon, and the large Maiden Castle.

Maiden Castle, in Dorset, England, remains one of the best-known extant hill forts. In its many archaeological layers, it clearly demonstrates how one culture built on another on the prehistoric hill forts. Excavated by Sir Mortimer Wheeler between 1934 and 1937, the Iron Age hill fort was initially developed from a single-rampart, 15-acre (6-hectare) enclosure in about the fourth century b.c.e. By the Roman conquest in the first century c.e., however, it had grown to an immense fortress made up of four concentric ramparts that enclosed nearly 45 acres (18 hectares). Maiden Castle is believed to have surrendered to the Second Roman Legion under Vespasian shortly before 45 c.e. Yet the mighty Maiden Castle was occupied in an earlier form long before this. Neolithic constructions at the site include a prehistoric camp, enclosed by concentric ditches, and an immense earthen mound 1,805 feet (550 meters) in length. In addition, the remains of a Romano-Celtic temple attest to the mighty hill fort’s later occupation by Romano-Britons in the fourth century c.e.

From the third century b.c.e., the expansive world of the La Tène Celts increasingly shrank until the early first century b.c.e., when Rome began to penetrate Celtic lands in Gaul (modern France). Julius Caesar first encountered the Celts in Gaul in 58 b.c.e., where he met little resistance until he finally engaged an army of united Celts under Vercingetorix at Alesia in 52 b.c.e. Victory for Caesar here meant the collapse of Celtic dominance of Gaul, which he finally subjugated in 51 b.c.e. Independent Celtic kingdoms were maintained in southern Britain until their conquest by Claudius in 43 c.e., and in Ireland and parts of Scotland up into the Middle Ages.

The Roman Empire’s occupation of western Europe instituted a strong central government and accelerated the development of unfortified oppida, resulting in the decline of independent hill forts such as the one in Dorset, England. The Celtic hill forts in unoccupied Ireland, however, remained in use for about another five hundred years. When the Romans were ousted from Britain in the fifth century c.e., some forts were again occupied by the native Britons as a defense against the invading Saxons. As Roman power declined, invading Germanic tribes—the Saxons, the Angles, and the Jutes—renewed their drive westward into the former Celtic lands. Only along the Atlantic fringe of Europe did Celtic culture survive in distinct form. The modern populations of Ireland, Scotland, Wales, Cornwall, and Brittany retain strong Celtic elements, and the sites of thousands of Celtic hill fort settlements are scattered throughout Europe.

• Audouze, Françoise, and Oliver Büchenschütz. Towns, Villages, and Countryside of Celtic Europe. Translated by Henry Cleere. Bloomington: Indiana University Press, 1992. A scholarly but approachable work detailing many aspects of Celtic life and history.
• Cunliffe, Barry. The Ancient Celts. New York: Oxford University Press, 1997. An excellent archaeologically based overview of Continental Celtic civilization.
• Cunliffe, Barry. English Heritage Book of Danebury. London: B. T. Batsford, 1993. Exposition of the popular Celtic archaeological site discovered under Heathrow airport. Covers the structures erected consecutively over five hundred years.
• Rankin, David. The Celts and the Classical World. Reprint. New York: Routledge, 1996. A very thorough assessment of the interactions between Celts and Romans from the Hallstatt era through the fall of Rome. Includes an appendix on recently discovered remains of a Roman trading outpost in southern Ireland which appears to contradict the truism that Rome never made it to Ireland.
• Sharples, Niall M. English Heritage Book of Maiden Castle. London: B. T. Batsford, 1991. Traces the history of the largest known Celtic Iron Age hill fort: Maiden Castle, in Dorset, England. Sharples also discusses the Celts’ abandonment of the fort after the Roman invasion.

Boudicca; Julius Caesar; Hadrian; Vercingetorix. Oppida, Celtic
Hill forts, Celtic