Cupola

In architecture, a cupola /ˈkjuːpələ/ 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 word derives, via Italian, from the lower Latin cupula (classical Latin cupella from the Greek κύπελλον kupellon) "small cup" (Latin cupa) indicating a vault resembling an upside down cup.

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.

The square, dome-like segment of a North American railroad train caboose, which contains the second-level or angel seats, is also called a cupola.

Cupola (disambiguation)

Cupola, a diminutive of the Latin cupa (barrel) and thus meaning 'little barrel', is used for dome-shaped items. Of similar meaning the word cupula is used for anatomical references.

Cupola (geometry)

In geometry, a cupola is a solid formed by joining two polygons, one (the base) with twice as many edges as the other, by an alternating band of isosceles triangles and rectangles. If the triangles are equilateral and the rectangles are squares, while the base and its opposite face are regular polygons, the triangular, square, and pentagonal cupolae all count among the Johnson solids, and can be formed by taking sections of the cuboctahedron, rhombicuboctahedron, and rhombicosidodecahedron, respectively.

A cupola can be seen as a prism where one of the polygons has been collapsed in half by merging alternate vertices.

A cupola can be given an extended Schläfli symbol {n} || t{n}, representing a regular polygon {n} joined by a parallel of its truncation, t{n} or {2n}.

Cupolae are a subclass of the prismatoids.

Examples

The above-mentioned three polyhedra are the only non-trivial convex cupolae with regular faces: The "hexagonal cupola" is a plane figure, and the triangular prism might be considered a "cupola" of degree 2 (the cupola of a line segment and a square). However, cupolae of higher-degree polygons may be constructed with irregular triangular and rectangular faces.