The remains of the castle can be visited
Frankenberg Castle

The Frankenberg Castle Ruin, once a spur castle, is located on the Schlossberg near Helmers in the Schmalkalden-Meiningen district of Thuringia. This medieval fortification, whose origins date back to the late 11th century, was once an important stronghold on an old trade route.
History+
The construction of Frankenberg Castle is dated to the late 11th to early 12th century, with its first documentary mention from 1137. At that time, it was owned by the Lords of Frankenstein, who named themselves after the castle. The castle served to protect a trade route that ran through the Rosatal valley. After the male line of the Frankensteins died out in 1293, the castle passed to the Counts of Henneberg-Schleusingen, who held it as a pledge.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Metilsteiner / CC BY 3.0 via Wikimedia Commons
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: 50.7295, 10.2954