In the east corner of the inner courtyard lies the original well, drilled vertically through of bedrock. The castle keep is surrounded by a ring wall which encloses the bailey. A further forecourt is enclosed by another ring wall. At the south side of this ring wall was the entrance to the estate. On 18 October 1356, a powerful earthquake shook the Rhine rift; the donjon collapsed onto the eastern and southeastern buildings. Beginning about 1370, large-scale reconstruction and expansion of the castle took place. The donjon was demolished, the entrance to the keep relocated and the northern shield wall was closed and raised. The entrance to the castle is now in the southwest corner, where it is protected by the south tower and an inner bailey.