The Fortress can be visited
Deal Castle

On the coast of Kent, England, Deal Castle is a fortress considered one of the best-preserved coastal fortifications built by King Henry VIII. It has unique, symmetrical architecture.
History+
The fortress was constructed as part of a defense program by Henry VIII, which included twenty castles and served to repel potential invasions from France and Spain. Deal Castle was completed in 1540, after only one year of construction. Together with Walmer Castle to the south and Sandown Castle to the north, it formed a strategic line to protect the coast from enemy landings.
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: 51.2194, 1.4035