The Drususstein is one of Mainz's most tangible Roman survivals, standing on the citadel hill above the old town. The battered stone monument is traditionally associated with the Roman general Drusus and helps pull Mainz back to its time as Mogontiacum, a major military base on the Rhine.
It is a short stop, but an important one if you are following Mainz beyond the cathedral and Chagall windows. Combine it with the citadel area, the Roman theatre, and the Landesmuseum's Roman material for a clearer picture of how deep the city's history runs.