Early Christian architecture emerged in the 4th century AD, following the legalization of Christianity in the Roman Empire. This style is characterized by the use of basilicas, which were large, rectangular buildings originally used for public gatherings. These structures often featured a central nave, side aisles, and an apse at one end, where the altar was located. Another significant element of early Christian architecture is the use of catacombs for burial purposes. These underground burial sites were often adorned with frescoes and symbols, reflecting the beliefs of early Christians. Overall, early Christian architecture laid the foundation for later styles, including Romanesque and Gothic.