Columbia subject headings:
Coast defenses--Italy--Tuscany.
Fortification--Italy--Tuscany.
Towers--Italy--Tuscany.
Harvard subject headings:
Coast defenses--Italy--Tuscany.
Fortification--Italy--Tuscany.
Towers--Italy--Tuscany.
Tuscany (Italy)--Coast defenses.
Princeton subject headings:
Coast defenses--Italy--Tuscany--History.
Fortification--Italy--Tuscany--History.
Towers--Italy--Tuscany--History.