Hagia Sofia was built between 532 and 537, as a Christian church. It has influenced architects ever since. The circular dome covering a square base was developed at the same time as the Basilica plan of the Early Christian churches, in Italy. The Byzantine dome was later adopted into Islamic architecture. However, the Roman dome was constructed differently. Romans placed their dome over a solid circle of walling, best seen in the example of the Pantheon in Rome, instead of using the pendentives (an architectural feature). However, one shared feature of the time between the two styles was the use of opaque glass mosaics in the interior decoration, covering the walls. The Hagia Sofia plan is basically an inscribed Greek cross. The hall has four piers at the corners of the square rising in circular arches to support a central dome by means of four pendentives. The upper galleries were used by the women, and were reached by steps inside the building. Much of Hagia Sofia's appeal comes from its size. The inside is dominated by the central dome over 30.5 metres in diameter. Today after about 1500 years of continue used, Hagia Sofia still dominates the skyline of the Bosphorus. It is truly a milestone, among the world’s greatest architectural achievements, a testament of the sophistication of the 6C Byzantine Empire.