The Castle can be visited
Museum
Altenstein Castle

In the Wartburg district of Thuringia, Altenstein Castle rises. Originally built as a residential castle for the Dukes of Meiningen and later expanded into a summer residence, it is now in a landscape.
History+
The origins of Altenstein date back to the Middle Ages, when a castle stood here, strategically located on an old road over the Thuringian Forest and owned by the noble family of Stein. In 1346, the complex passed to the Landgraves of Thuringia via the Lords of Frankenstein. An episode occurred in 1521 when Martin Luther was abducted nearby on his return from the Diet of Worms and taken to Wartburg Castle for his safety. Although Neuenstein Castle was destroyed in the Peasants' War, Altenstein remained intact. However, in the Second Margrave War in 1554, the castle was plundered and devastated, after which it was rebuilt in the Renaissance style. After a fire in 1733, the castle was rebuilt in 1736 as a Baroque country house.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Mobile Geschichte
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: 50.8351, 10.3492