The Watergate of the Roman fort is situated in the east wall of the outer bailey exactly opposite the Landgate, (main entrance), which is situated in the western wall, a path runs east to west between these two gates. The Watergate was probably rebuilt before the Norman Conquest, the interior face has a late Saxon arch.
The gateway was rebuilt in the 14th century and a new outer gate and upper storey were added. The gate had three floors, and has an internal stone spiral staircase.