The Castle can be visited
Lancaster Castle

Lancaster Castle is a medieval fortress located in the English county of Lancashire. Built on a hill previously utilized by the Romans, it is the oldest surviving structure in Lancaster.
History+
The castle's origins trace back to 79 AD, when the Romans established a fort at this site to oversee the River Lune. The current castle was likely constructed in the 1090s on the foundations of this Roman castellum, after William II established a permanent border with Scotland. Lancaster Castle was seized by King Henry I in 1102 following a failed rebellion and frequently changed hands in subsequent centuries, including ownership by David I of Scotland and later the English kings Henry II, Richard the Lionheart, and Prince John.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Maciek Wegrzyn
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: 54.0499, -2.8056