It was the great achievement of the Byzantine architects Isidorus and Anthemius, to transfer the weight of the dome to the pillars using arches and pendentives, the four triangular sections of masonry that fill the gaps between arches and dome, to create the illusion of an unsupported dome floating in space.
Isidorus and Anthemius made the dome look like it was floating in space by using arches and pendentives to support it.