The first Christians worshipped in the synagogue or in private homes. In 313, when Christians first received protection under Roman law, they adopted the building style of the Roman court of law. In western Europe, the rectangular Romanesque and medieval Gothic styles predominated until the Protestant Reformation, when the decorative interiors of many western churches were destroyed in order to simplify and brighten them. In the eastern Church, churches were built with square rather than rectangular proportions, and were topped by domes. Today, churches are built in a variety of architectural styles, using a wide range of materials. Specific styles are discussed in the articles on the different Christian traditions.
Early Christian worship in private homes required houses with at least one big room. To accommodate their growing size, a congregation would sometimes buy a house, owning it in common but registering the property in one person's name. This person was known as the custodian, or episcopus. The congregation would then convert the inside of the house into a large meeting room, thus creating "house churches," the first churches. To avoid persecution, early Christians attempted to keep the locations of house churches secret. When a congregation grew too large to meet in the church, they either split the congregation to meet in two separate places or met at some inconspicuous place outside the city.
Outside the city of Rome, Christians buried their dead in dug-out caves or underground cemeteries, called catacombs, which were sanctioned by the Roman authorities. A small group would assemble in the close confines of these catacombs for a burial or a remembrance of their dead.
When the Roman Emperor Constantine issued the Edict of Toleration in 313, Christians were no longer in peril from persecution and began to build large stone churches in the same architectural style as the Roman basilica or town hall. The basilica had a rectangular shape, with an apse at the far end where the chairman and the council sat. In the early churches, the bishop sat on a chair in the center of the apse, flanked by presbyters and deacons, facing west toward the congregation. The bishop's chair was called a kathedra, the Greek word for seat and the origin of "cathedral," the name of the bishop's church.
Since the Christians continued the Jewish practice of reading and explaining scripture, they soon arranged a raised platform, a pulpit, so that people could better hear the speaker. On another platform stood the bishop's seat, and in front of that, a wooden dining table to hold the bread and wine for the Eucharist. This table came to be called an altar, from the Latin altare, a reminder of the Jewish altar on which sacrifices were offered. The altar became the symbol of Christ, the sacred space in the church that was the center of attention and action.
Sometimes two arms were added to the basic rectangle of the basilica, one on each side of the end where the apse was located. This allowed more people to be able to view the altar and gave the building the shape of the Latin cross, which has three short upper parts and a long lower part. Because of its Roman origins, this style of church architecture came to be known as Romanesque, and predominated in the West until the 12th century.