As part of the Reiss-Engelhorn-Museen, the Mannheimer Zeughaus plays a significant role in the city's museum landscape. The building is located in Quadrat C5 in Mannheim's city centre.
The house was built from 1777 to 1779 on the orders of Elector Karl Theodor as an arsenal for the Palatine army; the design is by a contemporary architect and sculptor. It is regarded as the last major monumental building of the electoral building phase in Mannheim and documents the transition from late Baroque to early Classicism. Later the building served as a barracks and was increasingly used for civilian purposes during the 19th century.
In 1901 the Zeughaus became municipal property; from 1903 it housed a trade hall and the municipal pawn office, and as early as 1908 it was put to museum use. From 1925 the ground floor accommodated the Museum of Natural History, Ethnology and Prehistory. The building suffered considerable damage during the Second World War; provisional repairs were carried out from 1946, and exhibition space was available again from 1949. In 1953 the municipal council decided to establish a new museum in the Zeughaus; with funds from a foundation and following renovation, the Reiss-Museum opened in 1957.
In 1988 new buildings were erected on the neighbouring Quadrat D5 for archaeological as well as natural history and ethnological collections, which allowed the Zeughaus to make room for theatre and music history holdings as well as further art-historical collections and an exhibition on Mannheim's city history. After the city council decided on a comprehensive renovation in 2002, the general renovation and museum reconceptualization began in 2003. The reopening took place on 24 January 2007 for the city's 400th anniversary. The modernization cost €17.32 million; across roughly 6,000 square meters state-of-the-art museum technology, media installations and new exhibition concepts were implemented.