The Fort can be visited
FortressTenby
St Catherine's Fort

St Catherine's Fort is a Palmerston Fort located on St Catherine's Island, West Wales.
The Palmerston Fort is constructed of Granite and Limestone. It was built in 1870 on the orders of The Royal commission by Mr George Thomas of Orielton Terrace Pembroke.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Colin Jackson
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 51.6706, -4.6918