The Castle can be visited
Newcastle Castle

Newcastle Castle is a historic fortification in Newcastle upon Tyne, England, which gave the city its name. The complex features its stone keep, known as the Castle Keep, and the gatehouse, the Black Gate.
History+
The fortification dates back to Roman times, when a fort stood here to protect a bridge over the River Tyne. In 1080, Robert Curthose, a son of William the Conqueror, had a wooden motte built on this site, which became known as the “New Castle upon Tyne”. Between 1172 and 1177, King Henry II replaced this structure with a stone keep. King Henry III added the Black Gate to the fortification between 1247 and 1250. Although the city walls of Newcastle were built later in the 13th century, the keep and the Black Gate were not part of this fortification.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Newcastle_schloss.jpg
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: 54.9688, -1.6104