Section through Portico and Rotunda The section through the Pantheon shows in the darkened areas the thickness of the walls that support the dome. The dome itself gradually diminishes in thickness as it rises, as do the size and scale of the coffers, creating the perspective illusion of a much taller dome. The dome was constructed using a variety of materials, including concrete, volcanic tufa stone (a light weight material with great compressive strength), and brick arches. The base of the dome, where it want to spring outward, is buttressed by a series of stepped rings. The center of the domes is left open with an oculus, the only source of light within.