The Pantheon, in particular the interior of the Rotunda, has posed a paradox: unrestrained praise for its overall effect; severe criticism for its interior elevation. The criticisms were rooted in a Renaissance perception of Roman imperial architecture, a perception based too heavily on a Vitruvian view of Hellenistic trabeate architectural design, largely irrelevant to the Rotunda. This view of the critiques of San Gallo the Younger, Michelangelo, Desgodetz, and Viollet-le-Duc leads one to the Roman aims of the Roman architect who designed this interior. I wish to show how the Hadrianic state of the Rotunda may be taken as a projection of the Roman idea of the templum mundi.