The Castle can be visited
Brugg (Schwarzer Turm) Castle

The Black Tower, also known as Brugg Castle, is the oldest building in the Swiss city of Brugg. It stands on the northern edge of the old town, directly at a narrow point of the Aare River, which gave the city its name.
History+
The construction of the Black Tower took place in the last quarter of the 12th century, presumably at the behest of Count Albrecht III of Habsburg. The Habsburgs, whose ancestral seat was only a few kilometers away, temporarily used the city of Brugg, which emerged shortly thereafter, as their residence. The first documented mention of the tower dates back to 1238. For a long time, it was believed that the tower was of Roman origin, as material from the nearby Vindonissa legionary camp was reused for its construction.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Brugg_Turm_Aare.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: 47.4859, 8.2066