Hagia Sophia is famous for its gorgeous center dome that measures 31 meters in diameter and covers the naos with its half domes on the axis . The dome which rises about 55 meters from ground is sitting on four pendantives carried by four large arches . The pendantives are ornamented with a figure of four-winged angel . There are forty windows around the base of the dome which allows mystical reflections of light to illuminate the interior of the nave and gives the impression that the dome is hovering above the nave . The inside of the dome is ornamented with wonderful calligraphy . The building itself has two naves on each side , a boisterous apse and an inner and outer narthex following the entrance . From the entrance , one may proceed to the plain , non-colored outer (narthex) and then may pass to the inner (narthex) . The ceiling of the inner narthex is covered with non-figured mosaics and has two doors , the door at the north of inner narthex opens to the platform that goes to upper gallery while the other door on the south is the exit door and named Horologion . The main area of Hagia Sophia measures 73 . 5m x 69 . 5m and has about 107 columns . The columns are decorated and some of their headings carry the monograms of Emperor Justinian I and
Empress Theodora .
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