Columbia subject headings:
Palaces--Conservation and restoration--Italy--Viterbo--History--Sources.
Papal Palace (Viterbo, Italy)--History--Sources.
Popes--Dwellings--Italy--Viterbo--History--Sources.
Viterbo (Italy)--Buildings, structures, etc.
Harvard subject headings:
Architecture--Italy--Viterbo.
Palaces--Conservation and restoration--Italy--Viterbo.
Papal Palace (Viterbo, Italy)
Popes--Dwellings--Italy--Viterbo.
Viterbo (Italy)--Buildings, structures, etc.
Princeton subject headings:
Architecture, Italian--Italy--Viterbo.
Palaces--Conservation and restoration--Italy--Viterbo.
Papal Palace (Viterbo, Italy)
Popes--Dwellings--Italy--Viterbo.
Viterbo (Italy)--Buildings, structures, etc.