Who threatened the town and made such a huge task necessary? For about 70 years before the building of the town wall, the south-east coast of England had been raided by barbarian tribes from across the North Sea. These attacks became serious enough to warrant the building of three Roman forts along the Norfolk coast, at Brancaster, Caister-on-Sea and Burgh Castle.
Venta Icenorum, on the banks of the River Tas would have been a prime target for any raiding party that got past the naval and land patrols of the coastal forts. It was this long-term threat to the safety of the town that made the defences necessary.
A large ditch 80 feet (24.4m) wide by 17 feet (5m) deep was dug around the outside of the walls on three sides. This joined with the river to form a ring of defence around the town. The earth dug out from the ditch was probably used to build up the rampart (bank) behind the walls.
Only a few small areas of the original outer surface of the wall survive. You can see one of these towards the bottom of the wall in front of you. The main facing materials were large dressed flints laid in courses between bands of red tiles.
The only entrances into the town were through four heavily-guarded gateways. At regular intervals bastions (towers) were built out in front of the walls. These improved the view from the walkway along the length of the walls. The only exposed bastion can be seen near the river (near point 4). The remains of others are buried beneath the earth banks that have built up against the outside of the walls.