Inside the Pantheon's single-shell concrete dome is coffering which greatly decreases the weight. The vertical partitions of the coffering effectively serve as ribs, although this feature does not dominate visually. At the apex of the Pantheon's dome is an opening, 8 meters across. Brunelleschi was aware that a dome of enormous proportion could in fact be engineered without a keystone. The dome in Florence is supported by the eight large ribs and sixteen more internal ones holding a brick shell, with the bricks arranged in a herringbone manner. Although the techniques employed are different, in practice both domes comprise a thick network of ribs supporting very much lighter and thinner infilling. And both have a large opening at the top. 
One of the most widely copied features of Renaissance architecture were the great staircases from the chateaux of Blois and Chambord .  Blois had been the favourite residence of the French Kings throughout the renaissance. The Francis I wing, completed in 1524, of which the staircase is an integral part was one of the earliest examples of French Renaissance .  French renaissance architecture was a combination of the earlier Gothic style coupled with a strong Italian influence represented by arches, arcades, balustrading and, in general, a more flowing line of design than had been apparent in the earlier Gothic. The Chateau de Blois's triumphal staircase was imitated almost from the moment of its completion, and was certainly the predecessor of the "double staircase" (sometimes attributed to Leonardo da Vinci ) at the Château de Chambord just a few years later.
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