Basilica

Basilica, large structure in ancient Roman or early Christian times, usually built on a rectangular, as distinct from a circular or cruciform, plan. Later the term was conferred as an honour on certain churches selected by the popes, such as St Peter's Basilica in Rome.

Roman basilicas were used for law courts or for commerce. They consisted of a roofed hall entered from a portico at the side or end. The hall contained a wide central aisle, or nave, separated from two side aisles by rows of columns. The nave walls rose above the aisle roofs and were pierced with windows, forming a clerestory to admit light. At the far end of the nave was usually a raised platform, or bema, on which stood an altar. Behind the bema the hall terminated in a semicircular or polygonal area called an apse, which had seats for officials.

This basic plan had many variations. Some basilicas had a nave and four side aisles, as, for example, the basilica of Trajan (or Ulpia, 98-112), which also had a gallery and a semicircular apse at both ends. Others had no gallery or were almost square. Most had pitched roofs with wooden rafters, but some, such as the basilica of Constantine (or Maxentius, 310-313), had masonry vaults.

In the 4th century, when Christianity acquired imperial support, churches throughout the Roman Empire, such as Santa Maria Maggiore in Rome (432), were built on the basilica plan, usually over the grave of a saint. Many of them, notably San Clemente (11th century on a 4th-century foundation) and Old St Peter's (330, destroyed in the 16th century), both in Rome, were approached through a colonnaded atrium, or open court, like that of a Roman house. The basilica church consisted of an oblong space divided into a central nave and side aisles, sometimes with galleries. It was entered from one end through a porch, or narthex, beyond which penitents and those who had not undergone confirmation were not admitted. At the far end was the raised bema terminating in the domed apse, or sanctuary. In the centre of the sanctuary stood a canopied altar. Behind it was the bishop's chair facing the congregation, with seats for the presbyters and deacons on either side. Usually an area for the choir, surrounded by pierced screens and called the chancel, lay between the nave and the bema. The larger basilicas had wings, called transepts, flanking the chancel, to accommodate additional clergy.