Archaeological digs have revealed evidence of a Celtic settlement on the banks of the River Exe, but the modern-day city was built on the foundations laid by the Romans, who established Exeter as the administrative capital for the Dumnonii of Devon and Cornwall around AD50. The Romans built a fortified wall around the city, which was later improved by Alfred the Great as protection against Danish raids; parts of both the Roman and Saxon walls can still be seen at various points around the modern city. William the Conqueror laid siege to the city in 1067 and took 18 days to break through the walls. He appointed a Norman seigneur (feudal lord) to construct a castle, the ruins of which can still be seen in Rougemont and Northernhay Gardens.
Exeter was a major trading port until a weir was built across the river in 1290, halting river traffic. It wasn’t until 1563, when the first ship canal in Britain was dug to bypass the weir, that the city began to re-establish itself, especially through the cloth and wool trade.