The Petersberg Citadel is one of the largest and best preserved city fortresses in Europe, covering an area of 36 hectares in the north-west of the city centre. It was built from 1665 on Petersberg hill and was in military use until 1963. Since 1990, it has been significantly restored and is now open to the public as an historic site.Verein der Freunde der Citadelle Petersberg zu Erfurt e.V. (2015). 350 Jahre Zitadelle Petersberg. Tagungsband: Wissenschaftliches Kolloquim zum 350. Jahrestages der Grundsteinlegung der Zitadelle Petersberg vom 29. Mai bis 31 Mai 2015. Universität Erfurt.
