The Pantheon is the best preserved ancient building in Rome.
You actually have to go down to go in the building. As elsewhere in Rome the modern city is higher than the ancient city by a number of feet.
The massive bronze doors are orginal and are the oldest working pair in the world.
The back side exposes the arches constructed in the brickwork to distribute the weight of the dome.
The oculus or round opening has no glass and provides light - and rain - for the interior. The building was one of the first where the space formed by the structure was impressive as well as the walls themselves.
The inscription on the pediment references Caesar Marcus Agrippa, who built the orginal building.
Yes, you can get a Big Mac in Rome while looking at the Pantheon . Mc Donald's was everywhere I went.