As attested by many instances of rock art, the Northumberland region has a rich prehistory. Archeologists have studied a Mesolithic structure at Howick, which dates to 7500 BC and was identified as Britain's oldest house until it lost this title in 2010 when the discovery of the even older Star Carr house in North Yorkshire was announced, which dates to 8770 BC. They have also found tools, ornaments, building structures and cairns dating to the bronze and iron ages, when the area was occupied by Brythonic Celtic peoples who had migrated from continental Europe, most likely the Votadini whose territory stretched from Edinburgh and the Firth of Forth to Northumberland. It is not clear where the boundary between the Votadini and the other large tribe, the Brigantes, was, although it probably frequently shifted as a result of wars and as smaller tribes and communities changed allegiances. Unlike neighbouring tribes, Votadini farms were surrounded by large walls, banks and ditches and the people made offerings of fine metal objects, but never wore massive armlets. There are also at least three very large hillforts in their territory (Yeavering Bell, Eildon Hill and Traprain Law, the latter two now in Scotland), each was located on the top of a prominent hill or mountain. The hillforts may have been used for over a thousand years by this time as places of refuge and as places for meetings for political and religious ceremonies. Duddo Five Stones in North Northumberland and the Goatstones near Hadrian's Wall are stone circles dating from the Bronze Age.