Being thus Roman in the nature of their ground plan, it is not surprising to find that other portions of the early Christian buildings show decided characteristics of a Roman style. On the destruction of the Pagan temples by order of the Emperor Constantine about the year 330, much of their material was built into the earliest Christian churches, and the Roman character of their design being prevalent, they formed a style of architecture which has been designated Romanesque, of which the later styles, known here as Saxon and Norman were largely modifications. There is no reason to doubt that the earliest Christian churches were very unpretentious in form and that some time elapsed before there was anything which could be called a definite church architecture, beyond that to which we have alluded. Nevertheless, as the Church strengthened her position and grew in security, more attention was devoted to the subject of its edifices, and the departure in time from the original ground plan furnished an opportunity for the introduction of a more symbolical and appropriate design. The plan of the old basilica was abandoned for one in the form of the cross, the accepted symbol of the Christian religion, which departure, however, did not involve any very great alteration from the old ground plan. We come then to the time when one or other of the forms known as the Latin or the Greek cross--whichever was most convenient--was usually employed in a building designed for Christian worship, and these forms are universally found in the most elaborate structures of which the Christian Church can boast. As time passed, these cruciform churches were surmounted with a dome, steeple, or tower at the point where the members of the cross intersected each other. At first the most prominent of these external adornments was the dome; a characteristic of the architecture of Eastern Europe, which acquired the name Byzantine, from its having been carried to great perfection in Byzantium (Constantinople), the capital of the Eastern Empire. The church of S. Sophia, which was built, much as it now exists, early in the sixth century, and was afterwards converted into a mosque, is an almost perfect example of the Byzantine style. In this building we find the Roman arch used in a variety of ways, while the dome itself is formed entirely of this arch used as the crowning work of the edifice. Eastern churches in this style usually took the form of the Greek cross, this form being better calculated to support the weight of the cupola. In Western Europe, however, where the flat squat tower afterwards developed into the steeple, as we shall see in a later chapter, the Latin cross was mostly used, and this, with a few notable exceptions, is the plan of most western churches.