Columbia subject headings:
Basilica di San Pietro in Vaticano.
Rome (Italy)--History--476-1420.
Vatican City--Buildings, structures, etc.
Harvard subject headings:
Architecture, Medieval--Italy--Rome.
Basilica di San Pietro in Vaticano.
Church architecture--Vatican City.
Rome (Italy)--History--476-1420.
Rome (Italy)--History--To 476
Vatican City--Buildings, structures, etc.
Princeton subject headings:
Basilica di San Pietro in Vaticano.
Rome (Italy)--History--476-1420.
Vatican City--Buildings, structures, etc.