In Pagan practices the sacrifices and ceremonies usually occurred on the exterior.
Christianity was a mystery religion, and therefore needed to have a clear separation between the faithful and the non-faithful. This lead to a significant reorientation of religious architecture from the exterior to the interior which had meaning in all its expressed ways.
A centrally-open planned church has an altar at the center that was used for baptisteries or tombs.The sides of the building are of equal length and the main space is symmetrical when bisected laterally and longitudinally. A centrally-planned building may be square, circular, or polygonal. The most important feature of a centrally-planned building is the open space at the center of the building, developed around a vertical axis.
The Hagia Sophia is a prime example of Byzantine architecture, located in Istanbul, Turkey. The dome has the appearance of being suspended from heaven, which is considered the "Dome of Heaven". The clerestory windows placed beneath the dome allowed plenty of natural light to enter. The light illuminating on the gold mosaics throughout the interior created an ambiance of