In architecture, a cupola or lantern is a radially symmetrical ornamental structure (often dome-shaped or quadrilateral) located on top of a larger roof or dome, often used as a lookout or to admit light and provide ventilation. The word comes, through Italian, from the lower Latin cupula (classical Latin cupella from the Greek kupellon) small cup (lat. cupa) indicating a vault resembling an upside down cup.
In some cases, the entire main roof of a tower or spire can form a single cupola. More frequently, however, the cupola comprises a smaller structure which sits on top of the main roof. If the cupola can be reached by climbing a stairway inside the building, it is referred to as a belvedere or widow's walk. Some cupolas, called lanterns, have small windows which illuminate the areas below.
In the Victorian architecture, often seen in older homes of Upstate New York, New Jersey and northern Pennsylvania, especially in the Finger Lakes region, cupolas are often seen as a small room that extends above the main roof line. They may be square, rectangular, octagonal or round. In local folklore, they are regarded as Indian lookouts, but they may have also been created simply to offer a scenic view, which fits with the other name, belvedere, an Italian term denoting a fair view.
The term cupola is also often used for a projection above the roof of a barn, which is primarily there for ventilation purposes.