The presence of the fort built up an unplanned civilian community (vicus or canabae) of natives and the soldiers’ families, mostly to the northeast of the fort. This settlement served as the tribal capital (civitas) of the Dumnonii and was listed as one of their four cities (Greek: poleis) by Ptolemy in his Geography (it also appeared in the 7th-century Ravenna Cosmography, where it appears as an apparently confused entry for Scadu Namorum). When the fortress was abandoned around the year 75, its grounds were converted to civilian purposes: its very large bathhouse was demolished to make way for a forum and a basilica, and a smaller-scale bath was erected to the southeast. This area was excavated in the 1970s, but could not be maintained for public view owing to its proximity to the present-day cathedral. In January 2015, it was announced that Exeter Cathedral had launched a bid to restore the baths and open an underground centre for visitors. In the late 2nd century, the ditch and rampart defences around the old fortress were replaced by a bank and wall enclosing a much larger area, some 92 acres (37 ha). Although most of the visible structure is older, the course of the Roman wall was used for Exeter’s subsequent city walls. Thus about 70% of the Roman wall remains, and most of its route can be traced on foot. The Devonian Isca seems to have been most prosperous in the first half of the 4th century: more than a thousand Roman coins have been found around the city and there is evidence for copper and bronze working, a stock-yard, and markets for the livestock, crops, and pottery produced in the surrounding countryside. The dating of the coins so far discovered, however, suggests a rapid decline: virtually none have been discovered dated after the year 380. Bishop Ussher identified the Cair Pensa vel Coyt listed among the 28 cities of Britain by the History of the Britons as Isca, although David Nash Ford read it as a reference to Penselwood and thought it more likely to be Lindinis (modern Ilchester). Nothing is certainly known of Exeter from the time of the Roman withdrawal from Britain around the year 410 until the seventh century. By that time, the city was held by the Saxons, who had arrived in Exeter after defeating the British Dumnonians at Peonnum in Somerset in 658. It seems likely that the Saxons maintained a quarter of the city for the Britons under their own laws around present-day Bartholomew Street, which was known as “Britayne” Street until 1637 in memory of its former occupants.