The magnificent baroque Peterstor (Peter's Gate) has stood proudly at the main entrance to the citadel since the first years of construction (from 1665). It is adorned with the large official coat of arms of Johann Philipp von Schönborn (1605-1673), Archbishop of Mainz, Elector and builder of the fortress. The lower level within the main rampart is the gatehouse. This is where the casemates are located, i.e. bomb-proof, vaulted rooms surrounded by meter-thick walls for guards and guns. For defensive purposes, the gatehouse has two portcullis in the 20-metre-long passageway and was also secured with a drawbridge until 1874. In 1671, the gatehouse was built over with the commander's house as an additional storey.