The 2.2 kilometres of preserved city wall illustrate the defensibility and importance of the former Free Imperial City. Mühlhausen thus has an almost completely preserved defence system. At the same time, it is also one of the oldest non-Roman city walls in the German-speaking world, as some of its components date back to the early 13th century. The inner fortifications surrounds an area of 49 hectares, which is the second largest heritage area in Thuringia after Erfurt’s Old Town. Of the former four city gates, the Innere Frauentor, dating back to 1655, has been preserved to the present day. The other entrances – the Erfurter Tor, the Felchtaer Tor, and the Görmartor – were torn down in the 19th century due to the construction of wider street accesses to the city centre.

The inner wall can currently be explored over a length of 370 metres. Some of the numerous towers and rondels were later converted into pavilions. They house themed rooms on the historical use of the facilities and on protective measures in the urban settings. The viewing platform of the Rabenturm (Raven Tower, 34.2 metres) offers an impressive panoramic view over Mühlhausen and the surrounding area.

Only the slim tower of the Outer Frauentor from the 15th century still bears witness to the original 5.6 kilometres long outer city wall, which enclosed the suburbs and a total area of 182 hectares.