The remains of the Castle can be visited
Schwabsburg Castle

The Schwabsburg castle ruin is in the Schwabsburg district of the municipality of Nierstein in Rhineland-Palatinate. It was a Staufer stronghold on the Rhine.
History+
The founding of Schwabsburg is presumed to have been around 1210. Its first written mention occurred in 1257 in a royal document, underscoring its significance as a Staufer base of power on the Rhine. In the 14th century, the castle came into the possession of the Archbishop of Mainz for six decades as a pledge of the Empire, before subsequently becoming the property of the Electors Palatine. During the Thirty Years' War, the castle was destroyed by a Spanish army under General Spinola. In 1799, the complex was finally demolished after an auction.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://www.wehrbauten.de/thread.php?threadid=899&sid=246e8c9fdbfa80ccf9a3497b2adfd6ed
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: 49.8639, 8.3117