To be privately owned
Königsegg Castle (Ruin)

The Königsegg Ruin, once the ancestral seat of an important noble family, rises in the present-day district of Königsegg within the municipality of Guggenhausen. It bears witness to a long history and offers an insight into past times in Upper Swabia.
History+
Königsegg Castle was built by the Lords of Königsegg, a branch of the Lords of Fronhofen, as their ancestral seat. The complex was first mentioned in a document in 1251. Until the mid-19th century, specifically until 1850, the castle belonged to the municipality of Hoßkirch. Between the 16th and 17th centuries, the castle underwent extensive renovations. However, from the mid-17th century onwards, it was no longer inhabited by its owners.
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: 47.9250, 9.4561