Although the Pantheon was built during the reign of Augustus Caesar, he is not believed to have designed it. Instead, credit for building it is given to Agrippa, who was consul under Augustus.
The inside of the Pantheon is a perfect sphere and the height of the roof is exactly the same as its diameter.
The oculus was the only way of admitting any natural light to the interior of the building. It was also a way of allowing smoke from sacrificial fires to escape.
The Pantheon is now used as a Christian church.