Brunelleschi constructed two domes, one within the other, a practice that would later be followed by all the successive major domes, including those of Les Invalides in Paris and the United States Capitol in Washington. The outer dome protected the inner dome from the rain and allowed a higher and more majestic form. The frame of the dome is composed of twenty-eight horizontal and vertical marble ribs, or eperoni, eight of which are visible on the outside. Those visible on the outside are largely decorative, since the outer dome is supported by the structure of the inner dome. A narrow stairway runs upward between the two domes to the lantern on the top. Older examples of double-shelled domes include the 50m tall Dome of Soltaniyeh and the Mausoleum of Khoja Ahmed Yasawi.
Brunelleschi constructed two domes, one within the other, a practice that would later be followed by all the successive major domes, including those of Les Invalides in Paris and the United States Capitol in Washington. The outer dome protected the inner dome from the rain and allowed a higher and more majestic form. The frame of the dome is composed of twenty-eight horizontal and vertical marble ribs, or eperoni, eight of which are visible on the outside. Those visible on the outside are largely decorative, since the outer dome is supported by the structure of the inner dome. A narrow stairway runs upward between the two domes to the lantern on the top. Older examples of double-shelled domes include the 50m tall Dome of Soltaniyeh and the Mausoleum of Khoja Ahmed Yasawi.