On the outside of the semicircular building is the course of a former water Sergraben from the 12th century can be seen. This was in the course of The castle-like fortification of the Palatinate created by the Staufer was 16 meters wide and over five meters deep. As an element of the fortification was also access to the semicircular building via the imposing "Heidesheimer Tor" bricked up. A paved path today marks the early medieval one Guidance to the gate, which was originally flanked by towers, again. The green area with playground and the street above “Auf dem Graben "are based in their semicircular shape on the monu- mental semicircular construction of the Kaiserpfalz. This had a diameter of 89 meters.
A herb garden was laid out in 2012 opposite the Heidesheimer Tor. This is stocked with useful plants and fruit trees that are already in the Capitulare de villis, the estate ordinance of Charlemagne (747 / 48−814), be listed. The capitular served as a guide, like a the royal court in order to be able to visit the constantly traveling to be prepared for the ruler and his followers.
