This position immediately at the gates of the town opened a strategic gap, as an aggressor could use the hill for a raid into Mainz or for a cannonade.
The construction of the "Schweickhardtsburg" fortress under the supervision of cathedral vicar Adolph von Waldenburg during the years 1620-29 provisionally filled this gap and integrated the hill into the system of city walls.
The name of the irregularly pentagonal fortification honors the reigning monarch of that time, the prince-elector Johann Schweikhard von Kronberg.
Around 1655 prince-elector Johann Philipp von Schönborn initiated an improvement of the fortification of the entire town comprising bastions according to French type.
Above the gate in direction to the town, a building for the commander of the citadel was erected in 1696 by the order of Lothar Franz von Schönborn.
The citadel and its surroundings bear witness to the entire history of Mainz concentrated in one spot, going from the Roman cenotaph, the Drususstein (Drusus monument) via the fortress barracks and up to the World War II air raid shelters.