In brief
The Roman monument is understood through the arena and the surrounding visual spaces.
Useful to know
The Amphitheatre in El Jem, Tunisia, is a Roman monument from the third century. Its scale testifies to the importance of public spectacles and to the resource of the city in which it is built. [1]
On a plan, consider the arena and the location of the audience around it. It's a different spatial organization than a theater with a stage at one end. The outer arches are important, but they don't explain the whole building on their own. For a fuller reading, he traced how the entrances, the surrounding spaces and the viewing places created a common system for gathering and movement of people.
Sources
For further detail and to check the information: