The Castle can be visited
Heiligenberg Castle

Heiligenberg Castle, a Renaissance complex, stands on a high plateau in the Linzgau, north of Lake Constance. It remains to this day in the possession of the House of Fürstenberg.
History+
The origins of Heiligenberg Castle date back to the Middle Ages, when Count Berthold von Heiligenberg had a castle built around 1250. In 1277, the complex came into the possession of the Counts of Werdenberg, who expanded it in the late Middle Ages. Through the marriage of Countess Anna von Werdenberg to Count Friedrich zu Fürstenberg in 1516, the castle passed to the House of Fürstenberg in 1535. Shortly before his death in 1559, Friedrich decided to convert it into a Renaissance castle. Count Joachim von Fürstenberg (1538–1598) was the principal builder, transforming the medieval castle into a Renaissance palace with a new south wing and a Renaissance courtyard between 1560 and 1575. Under the direction of Hans Schwarz, the complex acquired its current appearance. Between 1580 and 1584, the Knights' Hall was created inside, featuring an intricately carved coffered ceiling by Jörg Schwartzenberger and fireplace structures likely by Hans Morinck.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://commons.wikimedia.org/wiki/File:Heiligenberg_039.JPG?uselang=de
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: 47.8167, 9.3100