Mainz City Hall has a gross floor area of approximately 23,500 m². Together with the City Hall garage in front, the City Hall plateau, and the bridge tower across Rheinstraße, all of which were built according to Jacobsen's designs, Mainz City Hall is part of a distinctive urban ensemble in the style of the late 1960s.

The interior is characterized by Jacobsen's design ideas in its wall-mounted furnishings and his designer furniture and lamps ("Ameise," "Schwan," "Munkegaard ceiling lights," "AJ lights") and can be described as a total work of art of this era, especially in the council chamber and meeting rooms.

Due to its artistic, scientific, and urban significance, the town hall and its interior were formally designated as a single monument under § 8 of the Monument Protection Act (DSchG) by administrative act on December 3, 2005. The entire ensemble of the town hall, town hall square, and bridge tower was also protected by a statutory order (RVO) dated June 31, 2006 (monument zone according to § 5 (1) DSchG).