The castle dates from 1153 but the visible ruins on the cliff above the sea are
from later additions. Over the years the town walls took over as the main defence of Tenby. Much of these 13th century walls survive, the most complete in Wales along with a round gateway, the West Gate, which was one of four entrances to the town. The castle was badly damaged during the Civil War.
St Catherine's Fort, built in 1869 as one of the Palmerston defences for Pembroke, is on a rocky outcrop in the middle of the beach below the castle. The fort never took part in any action. It was sold off in 1907, and has been privately owned since, although it is now derelict.