The remains of the Castle can be visited
Granegg Castel (Ruin)

The Granegg ruin, a former hilltop castle, sits on a mountain spur of the Kalten Feld in the municipality of Waldstetten in the Ostalb district, Baden-Württemberg.
History+
The construction of Granegg Castle is presumed to have taken place in the 13th century due to the bossed ashlar used, although exact construction dates and the identity of the builders are unknown. The original owners are also not clearly documented; only the Lords of Stoffeln and the Lords of Holtz are mentioned as possible castle lords. The castle, which strategically dominated the Christental pass, probably did not exist for very long and was abandoned by the 14th century at the latest.
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: 48.7299, 9.8406