In the Middle Ages, the Pantheon, the Roman Temple of all the gods, became a church. It was built by the Emperor Hadrian between AD118-128. The height and diameter of the rotunda are equal: 140 feet. The opening at the top, the oculus, provides the only light. When it rains, water comes through the oculus. It now houses the tomb of Raphael (since 1520) and several kings of modern Italy.
Addition: a friend just emailed me that a guard there told him when it rains, the water drains to the edges because the floor is slightly slanted and there are drains to take it away. Isn't it amazing that someone thought to do it that way almost 2000 years ago?
The coffered ceiling was used to reduce the weight of the dome, and greatly adds to the appearance. The spot of light off to the side of the oculus is a reflection.
I got only one view of the interior, as it was so dark inside. I had to lighten this one quite a bit to see the details.
A most surprising sight is this pyramid, built as a tomb by Caius Cestius (a Roman magistrate) in 30 BC. It is 118 feet high and took 330 days to build. In that time, Egyptian architecture was all the rage in Rome.
In the third century, the Emperor Aurelian incorporated it into a wall built around the seven hills of Rome to serve as a defense against marauding Germanic tribes. It is 11 miles around and has 18 gates and 381 towers.