Chester is the only city in the UK with a complete circuit of city walls still, more or less, intact. The walls first appeared as the perimeter fortifications for the Roman fort. Modified by the Normans after the conquest to run down to the river and the port of Chester. They became a promenade for the well to do of Chester during the 18th century.
The amphitheatre, beyond the city walls was the largest such construction in the British Isles. Though little remains today it is a potent indication of how important this location was to the Romans.