Alberti's design uses the idea of the triumphal arch, especially the triple-arched variety (Arch of Constantine) and the pediment from the classical temple (also sometimes incorporated in the triumphal arch). In addition, his rational design for the facade made the height equal to the width. He uses a central barrel vault over the entrance with lower barrel vaults at right angles in the loggia. The facade pilasters continue through three stories--the so-called "giant" order, used later by Michelangelo.
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The entrance barrel vault echoes the interior with its huge barrel vault while the loggia vaulting echoes the barrel vaulting in the chapels inside at right angels to the nave.
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