The Latin word basilica initially described a type of Roman building used as a principal public building for transacting business and legal matters with the magistrates conducting their business on a raised dais in the apse at the end of the building. These buildings were located usually at the forum in the center of Roman towns. With the legalization of Christianity the form of the basilica proved adaptable for Christian rites and was adopted for building large churches.
The basilica is a long rectangular building, with side aisles, that are separated from the central nave by columns. The nave is usually wider and sometimes higher than the aisles. Where the roof of the nave is higher than that of aisles, clerestory windows provide light directly into the nave area. In Christian usage the apse became the area of the altar. Notable classic examples of basilica style churches in eastern Europe include Hagia Sophia of Constantinople and St. Sophia of Kiev.