atrium, in architecture, an open central court originally of a Roman house and later of a Christian basilica. In domestic and commercial architecture, the concept of the atrium experienced a revival in the 20th century.

In Roman times the hearth was situated in the atrium. With the developing complexity of the domus (a more capacious residence), however, the kitchen and hearth were removed to other positions, and the atrium began to function as a formal reception room and as the official centre of family life. By the end of the Roman Republic, one or more colonnaded courts were added in the larger houses, removing from the atrium the last vestiges of family life. During the Roman Empire, the room virtually became the office of the owner of the house. Traditionally, the atrium held the altar to the family gods, the Lares. The atrium was designed either with or without columns; it had, universally, a marble basin known as the impluvium, which was situated in the centre of the room under the opening in the roof called the compluvium.

The term atrium is used in a generic sense (like the English hall) for both consecrated and unconsecrated buildings such as the Atrium Vestae, where the Vestal Virgins lived, and the Atrium Libertatis, the residence of the Roman censor. In Rome the word atrium also signified any open court surrounded by porticoes placed in front of a temple. The concept of an atrium was also adopted by the early Christians. An open court, or atrium, surrounded by colonnades or arcades was often built in front of a Christian basilica. The churches of San Clemente, Rome, and San Ambrogio, Milan, and the Basilica Eufrasiana of Parenzo (Poreč) in Istria (Croatia) still retain their atria.

Hagia Sophia. Istanbul, Turkey. Constantinople. Church of the Holy Wisdom. Church of the Divine Wisdom. Mosque.
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This article was most recently revised and updated by Naomi Blumberg.

Romanesque architecture, architectural style current in Europe from about the mid-11th century to the advent of Gothic architecture. A fusion of Roman, Carolingian and Ottonian, Byzantine, and local Germanic traditions, it was a product of the great expansion of monasticism in the 10th–11th century. Larger churches were needed to accommodate the numerous monks and priests, as well as the pilgrims who came to view saints’ relics. For the sake of fire resistance, masonry vaulting began to replace timber construction.

Romanesque churches characteristically incorporated semicircular arches for windows, doors, and arcades; barrel or groin vaults to support the roof of the nave; massive piers and walls, with few windows, to contain the outward thrust of the vaults; side aisles with galleries above them; a large tower over the crossing of nave and transept; and smaller towers at the church’s western end. French churches commonly expanded on the early Christian basilica plan, incorporating radiating chapels to accommodate more priests, ambulatories around the sanctuary apse for visiting pilgrims, and large transepts between the sanctuary and nave.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Alicja Zelazko.