The remains of the castle can be visited
New Gleichen Castle

The castle remains of Neue Gleichen are the remnants of a hilltop castle on one of the twin peaks of the Gleichen in the Göttingen district of Southern Lower Saxony. Together with the neighboring Alte Gleichen, it formed an ensemble that gave the municipality its name.
History+
The origins of Neue Gleichen Castle date back to the 12th century, when it was built around 1100 by the Counts of Reinhausen. They had previously converted their ancestral castle in Reinhausen into a collegiate church. Around 1270, it came into the possession of the Lords of Uslar, a ministerial family. Later, the Uslar family split into the Altengleichen and Neuengleichen lines.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: Roland Neubert, Halle (Saale)
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: 51.4704, 10.0401