A small tidal island off Castle Beach, joined to Tenby by a strip of sand at low tide. On top stands an imposing Victorian fort built in the 1860s as part of a chain of coastal defences against a feared French invasion that never came. The fort has been by turns a private house, a wartime gun emplacement, and a small zoo; today it opens for guided tours when restoration allows.
Even without going inside the fort, the walk across the sands at low tide and the rock pools at its base are worth the short detour. Check tide times before you go — the causeway is only safely walkable for a few hours each side of low water.