Grünsberg castle is situated on a sandstone outcrop raised above the Schwarzach Valley. The castle probably served as a a hiding place because, from the valley, it is detectable only in close proximity. Three sides of the castle are surrounded by very steep natural gorges. Only the west side, which nowadays adjoins the road and which constituted its weakest defensible point, was originally protected by a moat. There used to be a drawbridge spanning the moat. Around 1740 the drawbridge was replaced by a stone embankment. This existed until 1960 when it was sacrificed when a new road was constructed at a higher level.