The main piers which subdivide nave and side aisles are most interesting, as their greater portion belongs to the original structure. They are faced by semicircular shafts which carry simple, unmolded, transverse ribs in the central aisle. A small additional columnar section is seen in the angles of the piers, supporting in an awkward position, with the assistance of the interposed corbel, molded, diagonal vaulting ribs. Columns, reaching to about two thirds of the height of the tall shafts of the nave, carry the arches separating nave from side aisles. The undecorated base-molds of the total composite piers are all supported upon a heavy, widely projecting, common drum, a curious remnant of the earlier single Byzantine pillar of but one body and base. The capitals are among the great glories of the edifice. They are remarkable from every point of view, and among the finest Byzantine extant, comparable to the best of Saint Mark's or of Sancta Sofia. The acanthus leaves are carved with all the jewel-like sparkle and crispness and the play of light and shade of the best period; the life and spring of a living stem are in them. Their oriental parentage is apparent at a glance. Much of the carving is alive with all the fancy and imagination of the day,--beasts and monsters, real and mythical animals, masks and contorted human figures and devils interlace on the bells and peer out from the foliage. The execution is quite unrestrained. It has a divergency which must have had its unconscious origin in the different antique caps serving again in the early Byzantine edifices. The ancient carvers must have realized the full importance of sculptural relief in their poorly lighted edifices. Again, the corbels which carry the diagonal ribs are formed by crude contorted beings and animals, in some instances bearing figures leaning against the lower surfaces of the diagonal ribs and intended still further to conceal its faulty spring. At the intersections of the diagonal ribs are bosses with figures at the salient points.