The first settlement in the Brighton area was Whitehawk Camp, a Neolithic encampment on Whitehawk Hill which has been dated to between 3500 BC and 2700 BC. It is one of six causewayed enclosures in Sussex. Archaeologists have only partially explored it, but have found numerous burial mounds, tools and bones, suggesting it was a place of some importance. There was also a Bronze Age settlement at Coldean. Brythonic Celts arrived in Britain in the 7th century BC, and an important Brythonic settlement existed at Hollingbury Castle on Hollingbury Hill. This Celtic Iron Age encampment dates from the 3rd or 2nd century BC and is circumscribed by substantial earthwork outer walls with a diameter of . Cissbury Ring, roughly from Hollingbury, is suggested to have been the tribal "capital".