The remains of the Castle can be visited
Greiffenberg Castle

The Greiffenberg castle ruin, a former hilltop castle, marks the northern edge of the Greiffenberg district, which belongs to the town of Angermünde in the Uckermark region. Its history dates back to the 13th century.
History+
The origins of the castellan-like castle lie in the year 1224. As early as 1261, it was mentioned as the ancestral seat of the von Greiffenberg family, then as “civitas Grifenberg” with a hospital. After the confirmation of ownership by the Duke of Pomerania in 1349, the castle returned to the Margraviate of Brandenburg in 1354. In 1426, the Pomeranians conquered the complex, but by 1446, it once again belonged to the Margraviate of Brandenburg. From 1473 to 1803, the castle was owned by the von Sparr family, during which time it suffered destruction in the Thirty Years' War. From 1850 onwards, the castle passed into the possession of the Counts von Redern.
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: 53.0912, 13.9645