Hillforts are the most well-known Iron Age monuments found in much of central and southern England. They are also amongst the most impressive. Many consist of a single bank and ditch encircling a hilltop. These are known as univallate (single walled) hillforts. More impressive are the bivallate (double walled) or multivallate (many walled) hillforts with their rings of ditches and banks, or ramparts. These prominent sites often had complicated entranceways, which suggests that there was a need to defend the interior of the enclosure.

Defence is an obvious function for these sites, however, the interior of hillforts seems to have varied a great deal. Some, such as Danebury in Hampshire, appear to have had many houses, storage pits and granaries, ritual structures and even a street plan. Others seem to have been empty. This suggests that hillforts were different in different regions.

It was once thought that all hillforts were the strongholds of local chieftains. However, most excavated hillforts have yielded few high status artefacts and it is now thought that they were created and maintained by a local community. They might have been centres for communal grain storage, villages, or places for religious ceremonies and celebrations.