Columbia subject headings:
Architecture--Vatican City.
Fabbrica di San Pietro (Vatican City)--History.
Vatican City--Buildings, structures, etc.
Harvard subject headings:
Basilica di San Pietro in Vaticano.
City planning--Vatican City.
Vatican City--Buildings, structures, etc.
Princeton subject headings:
Architecture--Vatican City.
Fabbrica di San Pietro (Vatican City)--History.
Vatican City--Buildings, structures, etc.