The Pantheon was commissioned by Marcus Agrippa as a temple to all the gods of Ancient Rome and rebuilt by Emperor Hadrian
in about 126 A.D. to reflect the terrestrial and cosmic order. Almost two thousand years after it was built, the
Pantheon's dome is still the world's largest unreinforced concrete dome.

The oculus (central opening to the sky) at the dome's apex is a 30 foot hole and the only source of natural light and air for
the Pantheon. Throughout the day, the light from the oculus moves around this space in a sort of reverse sundial
effect. The oculus also serves as a cooling and ventilation system. During storms, a drainage system below
the floor handles the rain that falls through the oculus. The height to the oculus and the diameter
of the interior circle of the Pantheon are the same, 142 feet.