Columbia subject headings:
Architecture, Medieval--Conservation and restoration--Italy--Siena.
Church architecture--Italy--Siena.
Duomo di Siena.
Siena (Italy)--Buildings, structures, etc.
Harvard subject headings:
Architecture, Medieval--Conservation and restoration--Italy--Siena.
Church architecture--Italy--Siena.
Domes--Italy--Siena.
Duomo di Siena.
Siena (Italy)--Buildings, structures, etc.
Princeton subject headings:
Architecture, Medieval--Conservation and restoration--Italy--Siena.
Church architecture--Italy--Siena.
Duomo di Siena.
Siena (Italy)--Buildings, structures, etc.