Cupola

In architecture, a cupola /ˈkjuːpələ/, sometimes US: /ˈkpələ/,[1] is a relatively small, most often dome-like, tall structure on top of a building.[2] Often used to provide a lookout or to admit light and air, it usually crowns a larger roof or dome.[3][4]

Cupola
A cupola over a cella. "Cave with the Ring-Bearing Doves" (Cave 123) at the Kizil Caves, Xinjiang, China, 6th-7th century CE. Reconstitution in the Museum für Asiatische Kunst

The word derives, via Italian, from lower Latin cupula (classical Latin cupella from Greek κύπελλον kupellon) 'small cup' (Latin cupa) indicating a vault resembling an upside-down cup.[lower-alpha 1]