Hagia Sophia is covered by a central dome with a diameter of 31 meters (102 feet), slightly smaller than the Pantheon's. The dome seems rendered weightless by the unbroken arcade of arched windows under it, which help flood the colorful interior with light. The dome is carried on pendentives: four concave triangular sections of masonry which solve the problem of setting the circular base of a dome on a rectangular base. In Hagia Sophia the weight of the dome passes through the pendentives to four massive piers at the corners. Between them the dome seems to float upon four great arches.