In architecture, a cupola is a small, most often dome-like, structure on top of a building. Often used to provide a lookout or to admit light and air, it usually crowns a larger roof or dome.
The cupola is a development during the Renaissance of the oculus, an ancient device found in Roman architecture, but being weatherproof was superior for the wetter climates of northern Europe. The chhatri, seen in Indian architecture, fits the definition of a cupola when it is used atop a larger structure.
Cupolas often appear as small buildings in their own right. They often serve as a belfry, belvedere, or roof lantern above a main roof. In other cases they may crown a spire, tower, or turret. Barns often have cupolas for ventilation.
Cupolas on the towers of Montefiascone Cathedral, Italy.
Ribbed cupola crowns the minaret of the Mosque of Uqba, in Kairouan, Tunisia.
Inside of Armenian Orthodox church cupola in Lviv, Ukraine.
Cupolas were also used on some old barns for ventilation.
A cupola-style caboose with an "angel seat" above