The remains of the Castle can be visited
Nesselburg Castle (Ruin)

At approximately 1035 meters above the market town of Nesselwang in Ostallgäu stands the Nesselburg ruin, a former hilltop castle. Its remains date back to the late 13th century.
History+
The construction of Nesselburg took place towards the end of the 13th century by the Lords of Rettenberg. A first documentary mention dates back to 1302. Shortly after its foundation, the Rettenbergers pledged the dominion to the Prince-Bishopric of Augsburg, but received it back as a fief. From 1350, after the childless death of the last Rettenberger, Heinrich, the castle became the center of an administrative district (Pflegamt). During the Peasants' War in 1525, the administrative seat was plundered and set on fire, but subsequently restored.
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: 47.6119, 10.5026