Burg Grimnitz, Medieval castle ruin in Joachimsthal, Germany

Burg Grimnitz is a castle ruin situated on a sandy elevation between Werbellinsee and Grimnitzsee lakes in the Brandenburg region. The surviving vaulted cellars and foundation walls reveal the original structure and construction methods of the fortress.

Grimnitz Castle was first documented in 1297, though historians agree it already existed under the jointly ruling Ascanian margraves John I and Otto III of Brandenburg, serving as a hunting seat at the edge of the Schorfheide. It guarded the road between Werbellinsee and Grimnitzsee toward the Uckermark and Pomerania. After 1340 the castle fell into decay until Elector Joachim I had it restored in 1514 and modernized by builder Caspar Theiss. The 1529 inheritance treaty between Brandenburg and Pomerania was signed at Grimnitz.

The 1529 inheritance treaty between Brandenburg and Pomerania was signed at Grimnitz, settling succession claims between the two duchies. The ruin now belongs to the Grimnitzer Glashüttenverein, a local glassworks association that maintains the site and keeps alive the memory of the glassmakers who worked here.

The site is accessible on foot with direct access to the ruins and surrounding structures and foundations. Visitors should be prepared for outdoor conditions and sturdy footwear is recommended for exploring the uneven terrain.

The glassworks were set up between 1571 and 1584 by Leonhard Thurneysser, personal physician and court alchemist of Elector Johann Georg. The works moved several times within Joachimsthal before reaching Neugrimnitz north of Althüttendorf. Since then the ruin has belonged to the Grimnitz glassworks association, which owns it today.