What Is a Basilica?

A basilica is a type of public building, originally a Roman civic building used for the administration of justice and the conduct of public business, that was adapted by the Christian Church in the fourth century for use as a church. The Christian basilica is a longitudinal rectangular hall, typically with a central nave, side aisles, an apse at one end, and a clerestory that lights the central space. The building type was established in the Constantinian period of the early fourth century, became the standard church building of the Latin West, and remained the dominant church type in the Western tradition for more than a thousand years. For the broader context of early medieval church architecture, see early medieval architecture and early medieval art and architecture. The related discussion of pre-Romanesque architecture shows the development of the basilica plan in the post-Carolingian period, and the Byzantine counterpart to the basilica is treated in early Christian and Byzantine art.

The Roman Basilica

The Roman basilica was a large public building, typically rectangular in plan, with a central nave, side aisles, an apse at one end, and a clerestory. The building was used for the administration of justice, the conduct of public business, the housing of the law courts, and the gathering of the citizens of the Roman city. The basilica was a distinctive Roman building type, and the great basilicas of the Roman world — the Basilica Julia in the Roman Forum, the Basilica of Maxentius on the Via Sacra, the Basilica Ulpia in the Forum of Trajan, the Basilica of Constantine at Trier — are the major surviving examples.

The Roman basilica had several characteristic features. The central nave was typically a tall, well-lit hall, with the roof supported on columns or piers, and the side aisles were lower and narrower. The apse at one end of the building was the seat of the magistrate, and the open space in front of the apse was the place of judgment. The clerestory, a row of windows in the upper part of the wall, lit the central nave, and the timber roof was typically a simple truss or beam roof. The interior was often decorated with statues, painted plaster, and marble revetment.

The Christian Adaptation

The Christian Church adopted the basilica form in the early fourth century, in the context of the Christianization of the Roman Empire under Constantine. The Constantinian building program of the 320s and 330s established the Christian basilica as the standard church building of the Latin West, and the great basilicas of Rome — Old St. Peter’s, the Basilica of St. John Lateran, San Paolo fuori le mura, and Santa Maria Maggiore — were the major building projects. The same building type was adopted in the Holy Land, in North Africa, in the Balkans, and in the new churches of the Christian capitals.

The Christian adaptation of the basilica involved several changes. The apse, which in the Roman basilica was the seat of the magistrate, became the seat of the bishop and the focus of the Christian liturgy. The altar was placed in the apse, and the syntheticum (the curving bench for the clergy) was placed around the apse. The solea (the processional way from the nave to the altar) and the ambo (the raised platform for the readings) were added to the interior. The transept, the crossing, and the narthex were later additions that allowed for a more elaborate liturgical program. The result was the Christian basilica, a building type that was at once a public building, a liturgical space, and a sacred place.

The Christian Basilica Plan

The Christian basilica plan was standardized in the Constantinian and Theodosian periods and remained remarkably constant for centuries. The basic plan consists of a longitudinal rectangular hall, oriented east-west, with the apse at the east end, the entrance at the west end, the nave in the center, the side aisles on the north and south, and the transept (added later) at the east end of the nave. The central nave was typically lit by a clerestory, a row of windows in the upper part of the wall, and the apse was typically lit by a single large window, often placed behind the altar. The side aisles were typically separated from the central nave by a colonnade of columns or piers, and the interior was often decorated with mosaic, fresco, and marble revetment.

The proportions of the Christian basilica were typically long and narrow, with the length of the building often three or four times the width. The ratio of the central nave to the side aisles was typically 1:2 or 1:3, with the central nave tall enough to accommodate a clerestory. The apse was typically semicircular in plan, and the altar was placed in the center of the apse. The transept, when present, was typically as wide as the central nave, and the crossing — the intersection of the nave and the transept — was often crowned with a tower or a dome.

Major Surviving Examples

The major surviving examples of the Christian basilica include the great Constantinian and Theodosian basilicas of Rome, the basilicas of Ravenna, the great basilicas of the Holy Land, and the basilicas of the early medieval West. The Old St. Peter’s, the Basilica of St. John Lateran, the Basilica of Santa Maria Maggiore, the Basilica of San Paolo fuori le mura, the Basilica of San Lorenzo fuori le mura, and the Basilica of San Clemente are the major Roman examples. The basilicas of the Sant’Apollinare Nuovo and Sant’Apollinare in Classe at Ravenna are the major Ravennate examples. The Church of the Holy Sepulchre and the Church of the Nativity in Bethlehem are the major Holy Land examples.

The basilica form was also adopted in the post-imperial West, in the churches of the Anglo-Saxon kingdoms, the Carolingian Empire, the Ottonian Empire, and the regional traditions of the early medieval West. The surviving churches of the period — the Brixworth and Bradford-on-Avon churches in England, the Germigny-des-Prés church in France, the Ottonian churches of Germany — all show the influence of the Christian basilica form.

The Basilica in the Christian Liturgy

The Christian basilica was designed to accommodate the Christian liturgy. The plan of the basilica — the longitudinal nave, the central apse, the transept, the crossing, the narthex — was designed to support the procession of the clergy and the people from the entrance of the church to the altar, the celebration of the Eucharist at the altar, the reading of the Gospel at the ambo, and the singing of the psalms at the choir. The basilica was also designed to accommodate the catechumenate (the preparation of those to be baptized), the baptismal font (typically placed in the narthex or the baptistery), and the various liturgical feasts of the Christian year.

The basilica was a sacred space, and the Christian liturgy was designed to engage the senses of the worshipper. The architecture, the decoration, the music, the incense, the readings, the sermon, and the Eucharist all worked together to create a sacred environment that was at once physical, sensory, and spiritual. The basilica was the principal setting for the Christian liturgy, and the building type was the most important single development in the architectural history of the early Christian and medieval Church.