Keeping the enemy out

 Plan of the fort at Caister showing the defensive wall and ditches, the foundations of buildings and a surviving section of the remaining part of the road near the south gate. This map is based upon Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office © Crown copyright. Unauthorised reproduction infringes Crown copyright and may lead to prosecution or civil proceedings. English Heritage 100019088. 2007 The fort had a strong stone wall with an earth rampart behind it, forming a square with sides about 175m long. There were towers at the corners and at gates in the middle of each side.   The foundations of a small square guard room still remain, which formed the ground floor of one of the south gate's two towers and stretching away from it is the south wall.

There were two deep V-shaped ditches outside the wall.  An attacker crossing them would have been exposed to a hail of missiles from soldiers on the fort wall and towers.  Part of the inner ditch still remains, but the other lies buried under the modern road.

The defensive wall stood up to 5m high, built of mortared flint between courses of red tiles.  The modern entrance is on the site of a wooden bridge across the inner ditch to the south gate. (Drawing by Sue White) © English Heritage The fort had a garrison of between 500 and 1,000 men who fought against Rome's enemies on land and at sea.  By the 4th century, their main opponents were Anglo-Saxons from north-west Europe.  These raiders came silently in fast ships to plunder local settlements.