The term hill fort is commonly used by archeologists to describe the fortified enclosures, located to exploit a rise in elevation for defensive advantage. This fortification consists of one or more circular or sub-circular earth or stone ramparts, often with external ditches, following the contours of the hill.

Beyond this definition the variation in types and periods is wide. Some were also settlements whilst others appear only to have been occupied seasonally or in times of strife. Further, many hill forts, after careful archeological excavation, have been discovered to have been used not for military purposes, but to pen in cattle, horses, or other domesticated animals.

Hill forts are especially common across Europe. In Central Europe, hill-forts start with the late Neolithic, but are especially common in the Bronze Age Urnfield culture and in the Hallstatt culture of the early Iron Age, and were being built until the Roman conquest in many areas. Julius Caesar described the large late Iron Age hill forts he encountered during his campaigns as oppida. By this time the larger ones had become more like cities than fortresses and many were assimilated as Roman towns.

Britain and Ireland

Hill forts in Britain were used for habitation or as military encampments during the middle to late Iron Age, before the Roman Conquest, and then again following the end of Roman Britain, for a period of several decades into the Anglo-Saxon period. In Britain the great age of hill fort construction was between 200 BC and the Roman conquest in AD 43. Where Roman influence was less strong (for example, in uninvaded Ireland and unsubdued northern Scotland) hill forts were still built and used for several more centuries. Some hill forts were reoccupied by the Anglo-Saxons during the Viking invasions.

France

Well known French hillforts include Bibracte (Mont Beuvray) and Mont St. Odile (Mur Païen). The Gaulish hero Vercingetorix was famously besieged by Julius Caesar in the hill fort of Alesia.

New Zealand

The Maori people built hill forts, mostly in the country's North Island, during the Classic period (AD 1350-1800). Known as pa, the fortresses were sometimes sited atop extinct volcanoes and consisted of a settlement, sometimes even with cultivation plots, surrounded by ditches and banks. Wooden palisade fences ran atop the banks along with raised fighting platforms. During the Maori Wars, the design was gradually modified, with more below ground entrenchments, thick earthern ramparts and camouflage, to better resist British cannon.

Examples

Danebury, Hampshire
Dinas Emrys, Gwynedd
Eildon hill, Scottish Borders
Maiden Castle, Dorset
Mount Wellington, Auckland, New Zealand
Old Oswestry, Shropshire
Old Sarum, Wiltshire
South Cadbury, Somerset
Heuneburg, Germany
Traprain Law, East Lothian
Uffington Castle, Oxfordshire
The Wrekin, Shropshire