Exeter is a cathedral city in Devon, England. It lies within the ceremonial county of Devon, of which it is the county town as well as the home of Devon County Council. The city is on the River Exe about 37 miles (60 km) northeast of Plymouth and 70 miles (110 km) southwest of Bristol. Exeter was the most south-westerly Roman fortified settlement in Britain, although there is evidence a Cornish tribe existed in Exeter before the Roman invasion. Exeter became a religious centre during the Middle Ages and into the Tudor times: Exeter Cathedral, founded in the mid 11th century, became Anglican during the 16th-century English Reformation.