Among the most famous of Rome's wonders, the Pantheon is an iconic pagan site — and now a Catholic church. Sitting in the middle Rome, the Pantheon has become a hub of tourists and gelato shops. Very old, built in the 100's AD, the Pantheon was constructed by Emporer Hadrian.
From deconstructing the name "pantheon" it can be presumed that this temple was once dedicated to all the gods. However, "no cult is known to all of the gods and so the Pantheon may have been designed as a place where the emperor could make public appearances in a setting which reminded onlookers of his divine status". Built with a fascinating oculus and dome spiraling above the head of the onlooker, the structure is perfectly designed to house an enormous sphere.
Later adopted by the Christians and christened as the Basilica of Saint Mary of the Martyrs, the modern Pantheon houses the tombs of several Italian leaders, statues, and an ancient Byzantine Icon of the Virgin with Child that sent to the Pantheon in the 600's. Visitors are even welcome to attend mass at Saint Mary's, though you may have to communicate this to an Italian speaking guard who herds tourists away to make room for the mass-goers. This grandiose hub is essential for a visit to Rome, and it has the unbeatable price of being free — as with all churches.