Burg Schnellerts

Not so much a "Burg" (castle) anymore, but merely a ruin.
The castle on Schnellerts (the little mountain's name) was first built in the first half of the 13th century. Wiki and https://www.schnellerts.de/ give more background information, unfortunately only in German (but most browsers and Dr. Google can translate quite well nowadays).
On my main you can see a part of the wall surrounding the castle, and the remnants of the Bergfried (castle keep). It was 6.50m in diameter and the walls were 2.10m thick. The room in the middle, visible in the extra, was a dungeon, with little room for the prisoner, no light.
The ruin was not in good shape, but volunteers did a lot to restore it to a state that gives an impression of what it looked like, ages ago.

Thanks to Marlieske for hosting the Derelict Sunday challenge.