Columbia subject headings:
Architecture--Germany--Frankfurt am Main--History--20th century.
City planning--Germany--Frankfurt am Main--History--20th century.
Frankfurt am Main (Germany)--Buildings, structures, etc.
Main Tower (Frankfurt am Main, Germany)
Office buildings--Germany--Frankfurt am Main.
Harvard subject headings:
Architecture, Modern--20th century--Germany--Frankfurt am Main.
Architecture--Germany--Frankfurt am Main--History.
City planning--Germany--Frankfurt am Main--History--20th century.
Frankfurt am Main (Germany)--Buildings, structures, etc.
Main Tower (Frankfurt am Main, Germany)
Skyscrapers--Germany--Frankfurt am Main.
Princeton subject headings:
Architecture--Germany--Frankfurt am Main--20th century.
City planning--Germany--Frankfurt am Main--History--20th century.
Frankfurt am Main (Germany)--Buildings, structures, etc.
Main Tower (Frankfurt am Main, Germany)
Office buildings--Germany--Frankfurt am Main.