Tenby castle occupied a large steep-sided promontory attached by a narrow neck to the medieval borough with its splendid walls (see NPRN 33213). The castle is greatly ruined and only fragments remain within a public park.
The promontory was walled where it faces the town. It is reached by a sloping roadway rising along the southern wall. The much ruined gate has a D-plan barbican or outwork. Next to this the town museum built in the shell of the castle apartments. On the highest part of the promontory is a small round tower with a square stair turret. At 5.8m diameter this is the smallest castle great tower in Wales and may have been built as a homage to the great tower at Pembroke Castle.

John Wiles, RCAHMW, 03 November 2007