Near the town centre is Maumbury Rings, an ancient British earthwork converted by the Romans for use as an amphitheatre, and to the north west is Poundbury Hill, another pre-Roman fortification. There is little evidence to show whether or not Durnovaria survived into the post-Roman era: Gildas' record of a tradition, given in "De Excidio et Conquestu Britanniae" iii, of twenty-eight cities and sundry castles of former happy times was not provided with any names. Surviving northern boundaries of the administrative region, or "civitas" that included Dorset, reached as far as Selwood, and mark the county division between Somerset and Wiltshire to this day. In the sub-Roman period, as urban centres were progressively abandoned, the centres of administration and justice, such as they were, generally removed to fortified strongholds. The city's site is attested as "Dornwaraceaster" in the ninth century, elided to produce Dornaceaster", first recorded in 937.