The remains of the Castle can be visited
Château de Landskron

Château de Landskron, a ruin, is located on the Landskronberg near the Swiss border in the French commune of Leymen.
History+
The origins of Landskron Castle likely date back to the early 11th century, with its first documented mention in 1297. In 1504, the castle came into the possession of the Margraves of Baden, who had it converted into a fortress around 1515. During the Thirty Years' War, Landskron was occupied by Swedish troops in 1639 and subsequently handed over to their French allies. Contrary to initial agreements, the French did not return the castle even after the Peace of Westphalia, but instead transformed it into a border fortress and state prison from 1690 under the direction of Vauban. This prison, which held political prisoners and the mentally ill, existed until the French Revolution. One of its inmates was Bernard Duvergez de Soubardon, who spent over two decades there. In December 1813, Bavarian and Austrian troops captured the castle during the Napoleonic Wars of Liberation after a three-day siege. It was largely destroyed by fire and subsequently blown up.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Castle-Landskron-1781.jpg
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: 47.4885, 7.4907