Columbia subject headings:
Castles--Germany--Würzburg--History.
Fortification--Germany--Würzburg--History.
Würzburg (Germany)--Buildings, structures, etc.
Harvard subject headings:
Castles--Germany--Würzburg--History.
Festung Marienberg (Würzburg, Germany)--History.
Fortification--Germany--Würzburg--History.
Würzburg (Germany)--Buildings, structures, etc.
Princeton subject headings: