The sally port or escape port was a concealed exit from the fortification, built into the already existing curtain wall in the course of the 18th century. It was used for escape from the citadel, clandestine reconnaissance or surprise fallouts. Around 1830 the poterne was provided with a new upper entrance portal. In 1999/2000 the buried escape poterne was uncovered again and today it is another entrance to the fortress.