The remains of the Castle can be visited
Mühlburg Castle

The Mühlburg castle ruin, situated on a spur of the Schlossleite, is a structure in Thuringia. It is considered the oldest of the "Drei Gleichen" and ranks among the oldest preserved structures in the region.
History+
The first documented mention of Mühlburg dates back to May 1, 704, when Duke Hedan II gifted the "Castello Mulenberge" to Bishop Willibrord of Utrecht. Whether the complex already stood at its current location is not certain. In the year 1000, the spur castle came into the possession of the Counts of Orlamünde. Emperor Henry IV besieged it unsuccessfully in 1088. From 1130, it belonged to the Archbishopric of Mainz, which enfeoffed the Meinharde family with the castle. They subsequently called themselves Counts of Mühlburg and acquired Veste Wachsenburg in 1220. After the extinction of the Meinharde family in 1242, Mainz reclaimed the fief. In 1357, the citizens of Erfurt acquired the castle and fortified it into a stronghold, which secured trade routes until 1590.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Joachim Schneeleopard
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: 50.8689, 10.8322