The remains of the Castle can be visited
Urquhart Castle

Urquhart Castle, a castle ruin on the shores of Scotland's Loch Ness, was once one of the largest fortresses in the country.
History+
The site's origins date back to before the 6th century, with evidence of an earlier fortification. The castle was built around 1230 and developed into one of Scotland's largest complexes. In 1296, it temporarily fell to the English before coming under the control of the Scottish King Robert the Bruce. During the Wars of Independence, the castle was expanded into a medieval fortress, including a heavily fortified gatehouse and a keep.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Urquhart_Castle_distance_2.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: 57.3240, -4.4420