The Fortress can be visited
Walmer Castle

On the coast of Kent, England, south of the town of Deal, lies Walmer Castle, a well-preserved fortress. It is among the coastal fortifications built under King Henry VIII.
History+
The fortress was constructed between 1539 and 1540 as part of a defense system of twenty castles commissioned by Henry VIII to protect against potential invasions from Spain or France. Along with Deal Castle and Sandown Castle, Walmer Castle was intended to secure the coastal stretch off The Downs. The only military engagement the fortress saw occurred in 1648 during the English Civil War, when it was captured by Parliamentarian forces after a three-week siege, having previously been held by Royalists.
Source: Wikipedia · Licence: CC BY-SA 4.0
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: 51.2006, 1.4020