When Michelangelo saw this wonder for the first time he said that it looks more like the work of angels, not humans.
The Pantheon was originally built in 27 BC as a temple to honor all Greek Gods. It burned down several times, but was rebuilt and as we see it today in 120 AD. It is the best preserved Ancient Roman monument. It was turned into a church in 609 AD. The exact composition of the material is still unknown but is structurally similar to modern day concrete.
The most fascinating part of the Pantheon is its giant dome, with its famous hole in the top. The dome remains the largest unsupported dome in the world. The diameter of the dome is 142ft and is in perfect proportion which is the same measurement from the floor to the top of the dome.
There are no windows inside except the large oculus. The Pantheon now contains the tombs of the famous artist Raphael and of several Italian Kings and poets. The marble floor, which features a design consisting of a series of geometric patterns, is still the ancient Roman original.