A cupola is a type of what architectural feature?

In architecture, a cupola is a relatively small, most often dome-like, tall 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 word derives, via Italian language. In Italian “cupola” simply means dome, the ornamental top element is called “lanterna”. Italian, from lower Latin 'cupula' (classical Latin 'cupella'), from Ancient Greek κύπελλον ('kúpellon') 'small cup' (Latin 'cupa'), indicating a vault resembling an upside-down cup.

The cupola evolved during the Renaissance from the older oculus. Being weatherproof, the cupola was better suited to the wetter climates of northern Europe. Cupolas 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.