Dome is a hemispherical or curved roof structure that has crowned the most ambitious buildings of every civilisation that learned to build one.
The dome is a roof structure whose horizontal cross-section is approximately circular and whose form rises to a single point or surface. Roman engineers perfected the unreinforced concrete dome with the Pantheon (c. 126 CE), whose oculus-pierced span of 43 metres remained the world's largest masonry dome for over 1,300 years. The Byzantine dome of Hagia Sophia in Constantinople (537 CE) introduced the pendentive, a curved triangular surface that allowed a circular dome to sit on a square plan. The Islamic architectural tradition adapted the dome for mosques and mausolea — the Dome of the Rock in Jerusalem (691), the Süleymaniye in Istanbul (1557, by Sinan), the Taj Mahal (completed 1653). In Renaissance Florence, Filippo Brunelleschi's double-shell brick dome for Santa Maria del Fiore (1420–1436) solved engineering problems that had defeated builders for over a century, using a self-supporting herringbone brick pattern that needed no centring. Michelangelo's dome for St Peter's, the dome of the United States Capitol, the geodesic domes of Buckminster Fuller — every era's most ambitious public buildings have reached for the form.