An oculus (plural oculi, from Latin ', 'eye') is a circular opening in the center of a dome or in a wall. Originating in antiquity, it is a feature of Byzantine and Neoclassical architecture. It is also known as an ''œil-de-boeuf'' from the French, or simply a "bull's-eye".

Classical example

The oculus was used by the Ancient Romans, one of the finest examples being that in the dome of the Pantheon. Open to the weather, it allows rain to enter and fall to the floor, where it is carried away through drains. Though the opening looks small, it actually has a diameter of , allowing it to light the building.

Byzantine architecture

The oculus was widely used in the architecture of the Byzantine Empire. It was applied to buildings in Syria in the 5th and 6th centuries and again in the 10th century. In Constantinople's Myrelaion Church (c. 920), there are two oculi above the stringcourse on both lateral facades.

Neoclassical revival

Early examples of the oculus in Renaissance architecture can be seen in Florence Cathedral, in the nave clerestory and topping the crowns of the arcade arches. Since the revival of dome construction beginning in the Italian Renaissance, open oculi have been replaced by light-transmitting cupolas and other round windows, openings, and skylights. They can be seen in the pediments of Palladio's Villa Rotonda, though not in the dome. Use of oculus windows became more popular in Baroque architecture. Widely used by Neo-Palladian architects including Colen Campbell, one can be seen in the dome of Thomas Jefferson's Rotunda at the University of Virginia. Image:Wambierzyce - Basilica of the Visitation of Our Lady - ceiling 2.jpg|Effect of the view into a cupola through an oculus under natural light (Wambierzyce, Poland) Image:Oculus of mercury.jpg|Detail of oculus set in a cartouche with the head of Mercury (Beaux-Arts New York and New Jersey Telephone Company Building, Brooklyn) Image:Plafond hasht behesht esfahan.jpg|View of an oculus opening into a cupola in the Hasht Behesht, Isfahan (1699) File:Iglesia Parroquial de San Pedro, Calasparra, Región de Murcia, España.jpg|Oculi in San Pedro, Calasparra, Spain File:Museo de la Luz.jpg|Facade of the Colegio Grande, completed in 1749, of the San Ildefonso College, in Mexico City, Mexico


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{{wiktionary-inline Category:Ceilings Category:Domes Category:Roofs Category:Windows Category:Architectural elements