A church building is a building where Christians hold their religious services. Many church buildings are monuments and in most Western cities and towns the church is centrally located in the center. An important incentive for church building was Constantine the Great's Edict of Milan in 313, which legalized the Christian church in the Roman Empire. The first churches are characterized by a wide variety of shapes, but from the second half of the 4th century the basilica becomes the most common building type. Church building in the Eastern Roman Empire is characterized by a tendency towards central construction. From the end of the First World War, the development of church building largely coincided with that of architecture.