This engraving shows the rhythm of two tiers of smaller arches below the four great arches that support the dome. View from south. The lower wall and semidones gradually rise up toward the central dome. Interior, northwest pier with flanking exedrae and semidomes. The four piers are surprisingly slender.
Light enters through many windows.
The pendentives form a transition between the central square, described by four piers, and the circular base of the dome. Interior of dome. Interior of dome. This broader view shows all four pendentives and three of the semidomes. Interior, South wall.