The Linked Geometries of the Roman Pantheon and Hadrian’s Serapeum in Tivoli, Part II: The Serapeum

Abstract Although the Serapeum of Hadrian’s Villa differs from the Roman Pantheon in many respects, we demonstrate that their ground plans resemble each other to a surprising degree, since both incorporate combinations of octagonal and heptagonal symmetry, along with some of the same governing dimensions. However, the straightforward semicircular geometry of the Serapeum plan differs markedly from the more complex ellipsoid-based geometry of its unusual, segmented dome. It is thus tempting to imagine that the structure was designed in two phases: the first led by builders closely associated with the Pantheon project; and the second led by more experimental designers inspired or endorsed by Hadrian himself.