An oculus (plural oculi, from Latin oculus, 'eye') is a circular opening in the centre 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 "bulls-eye". The oculus was used by the 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 27 ft (8.2 m) allowing it to light the building just as the sun lights the earth. The rain also keeps the building cool during the hot summer months. Pliny in his Natural history call counters also oculus, oculi. 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 Constantinoples Myrelaion Church (c. 920), there are two oculi above the stringcourse on both lateral facades.