Semi-circular building (Defence wall)

The appearance of the imperial palace changed during the reign of the Hohenstaufen dynasty in the 12th century. This fundamental change is particularly evident at the Heidesheim Gate. The gate in the semi-circular building was walled up and replaced by a defence wall. The towers on the outer façade of the semi-circular building were also demolished as they were probably not useful or even a hindrance for defence purposes.

The previously open palace complex was sealed off on all sides with high walls and equipped with battlements and embrasures for fighting. In addition, the base area of the complex was extended to the south and also surrounded by a defence wall (outer bailey). The walled fortification was additionally secured on the outside by a system of ditches. A 5 metre deep pointed ditch was created on the outside of the semi-circular building, which can still be seen today in the green area in front of the Heidesheim Gate.

This remodelling changed the function of the imperial palace forever: The representative palace became a castle that served to enforce and secure Hohenstaufen territorial policy.