The Castle can be visited
Chepstow Castle

In Monmouthshire, Wales, Chepstow Castle is an example of Norman military architecture. It is considered the oldest surviving stone fortification in Great Britain.
History+
The construction of Chepstow Castle began in 1067 under the command of the Norman lord William FitzOsbern, making it one of the first stone castles built on the British Isles. The rectangular main tower, also known as the Keep, remains to this day. In the 13th century, the complex underwent extensive expansions and modernizations. The distinctive gatehouse also dates from this period.
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: 51.6441, -2.6748