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

In Kirberg, Hesse, the Kirberg Ruin stands on a rock. Its history is marked by an unusual joint construction project between two noble families, born out of a feud, which once granted Kirberg town rights.
History+
Around the year 1355, the Counts Gerhard von Diez and Johann von Nassau-Merenberg began construction of Kirberg Castle. This joint decision was the result of an arbitration that ended a feud over supremacy in Kirberg. The new fortress was built on a phonolite rock, where a church from 790 had previously stood. Simultaneously with the castle, a church and a ring wall were built for Kirberg, which also received town rights at that time. However, the use of the complex did not last long. By 1500, its condition was already described as poor. Although it occasionally served as accommodation for regional lords until the end of the 16th century and a guard was present until 1670, decay set in. In 1673, a pleasure garden was laid out on the rock.
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: 50.3104, 8.1560