The remains of the Castle can be visited
Heinzenberg Castle (Ruin)

The Heinzenberg ruin, a former fortress, is perched on a rocky hill below the village of Präz in the Swiss canton of Graubünden. It is characterized by its strategic location and the visible remains of a distinctive tower, which was once an important part of its defensive architecture.
History+
The exact circumstances of the construction of Heinzenberg Castle are not documented, but its origin is presumed to be around the year 1200, likely by the Barons of Vaz, who exercised jurisdiction in this region. The name Heinzenberg may have originally been a field name that later transferred to the castle and the entire valley side. In 1337, the castle passed by inheritance to the Werdenberg-Sargans family. Johann von Werdenberg sold his rights to Heinzenberg in 1383 to Ulrich Brun von Rhäzüns. Although the castle was not explicitly mentioned in this sale, it was in the possession of the Rhäzünsers by 1394 at the latest. During the Schams Feud in 1451, the complex was captured but, unlike many other castles, remained undestroyed.
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: 46.7399, 9.4087