The Pantheon dates back to 118 A.D. when it was built by the Emperor Hadrian, dedicating it to the worship of every god where it remained that way until 609. It was then converted into a Christian Church, and finally in 1870 it was turned into a memorial for the kings of Italy. Today visitors to Rome have the chance to visit this stunning piece of architecture for free. It remains an active church to this day, so it will be closed on some national holidays, or if a mass is taking place, but otherwise it is open from 8:30 until 7:30 pm. What most people love about the Pantheon is the oculus, the round opening in the centre of the dome that lets the sunlight in. It is in fact the only way for natural light to get into this church, and is a whopping 27 ft in diameter. Take your time inside and look at the tombs that are set into the walls, the details in the architecture, and if it happens to be raining, look down and watch the water virtually disappear. Beautiful, peaceful and an absolute must see when in Rome.