Some decades after the fort wall was constructed by the Roman army, it was supplemented with a small number of projecting towers or 'bastions'. These strengthened the walls and provided high vantage points in terms of visability and defence.
One of the bastions was placed across the remains of rooms 5 and 6 of the Painted House; the lower 4-6 feet of the bastion still survives.
Because it was constructed some decades after the wall, the construction of the bastion is quite different in form. Its external face consists of flint and sandstone, with two courses of tiles.
Traces of the Painted House can be seen projecting from beneath the plinth of the bastion.