Columbia subject headings:
Architecture--Italy--Siena--20th century--Congresses.
Architecture--Italy--Siena--Designs and plans--Congresses.
Harvard subject headings:
Architecture--Italy--Siena--20th century.
Architecture--Italy--Siena--21st century.
Architecture--Italy--Siena--Designs and plans--Congresses.
Architecture--Italy--Siena--History--Congresses.
City planning--Italy--Siena.
Siena (Italy)--Buildings, structures, etc.
Princeton subject headings: