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

On a rocky spur on the left bank of the Breg between Furtwangen and Wolterdingen stands the Zindelstein ruin, a former hilltop castle. Its first documented mention occurred in 1225.
History+
The origins of Zindelstein Castle likely date back to the 12th century, when it was probably built by the Counts of Zähringen. After the death of the last Zähringen Duke, Berthold V, ownership passed to the Counts of Urach, who subsequently called themselves Counts of Freiburg. In the 13th century, the castle came into the possession of the House of Fürstenberg, and in the 14th century, Count Hugo von Fürstenberg was its owner. With the construction of Neu-Fürstenberg Castle further west by the Fürstenbergs, Zindelstein lost its importance and was increasingly referred to as a castle site.
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: 47.9860, 8.3833