Columbia subject headings:
Harvard subject headings:
Castles--Germany--Mainz (Rhineland-Palatinate)--History.
Fortification--Germany--Mainz (Rhineland-Palatinate)--History.
Mainz (Rhineland-Palatinate, Germany)--Buildings, structures, etc.
Mainz (Rhineland-Palatinate, Germany)--History
Princeton subject headings:
Festung Mainz (Mainz, Germany)--History.
Military architecture--Conservation and restoration--Germany--Mainz (Rhineland-Palatinate)