dôme

Dôme, in architecture, refers to a rounded vault that forms the roof or ceiling of a space. Most domes are hemispherical or gently ovoid, though there are pointed or ribbed varieties. They are often set on a drum and used to span large interiors without columns, and they can be freestanding or part of a larger structural system such as a rotunda.

Structurally, domes transfer weight to the supporting walls or to a system of pendentives or squinches that adapts a circular base to a square or polygonal one. They may be solid masonry or built in shells with ribs, frames, or multiple layers. In modern construction, reinforced concrete, steel, or tensioned membranes often support domes, sometimes with glazing to admit light.

Types include hemispherical domes, onion domes, ribbed domes, and geodesic or double-shell domes. Onion domes are associated with Russian and Byzantine-inspired architecture, while geodesic domes emphasize modularity and light weight.

Notable examples: the Pantheon in Rome, Hagia Sophia in Istanbul, Dome of the Rock in Jerusalem, St. Peter's Basilica in Vatican City, and the Capitol dome in Washington, D.C. Domes have wide symbolic and functional roles, serving as ceremonial and civic landmarks and as architectural expressions of shelter, light, and the sky.