The Pantheon in Rome is an ideal case study for understanding classical space, orders, composition, light, and character. Despite having been compromised by additions and restorations over the years, the great domed temple remains today the most complete and best-preserved monumental interior to survive from Roman times. No better model will be found to illustrate the principles of classical interior architecture.
Upon entering the Pantheon, before we notice any particular details of the bounding walls or domed ceiling, we are impressed by the sense of space. Clearly, for the Roman architects, three-dimensional space was more than a void between objects. They conceived of space as positive, as if it were a solid body. In the classical conception, space is always volume, a geometrical solid, and a metaphor of the human body.
The basic unit of classical space is the room, and we should think of it not as a void but as an expansive, albeit insubstantial and invisible, mass. A room may always be described in terms of one or more geometrical solids, and its bounding surfaces — walls, ceiling, and floor — are also figures derived from Euclidean geometry. The Pantheon is designed in the form of a sphere inscribed within a cylinder. >>>