Pantheon, which means "every God", is a temple to all the gods of Ancient Rome.It is adjacent to the Piazza della Rotonda and is one of the glories of the Roman Empire.It consists of two parts - a porch or portico and an ornate, massive rotunda capped by a spectacular dome and oculus.The Pantheon's dome is 150' high and is one of the spectacular constructions of the Roman Empire.The oculus(an opening) served three purposes. One, an exclusion of weight helps in reducing the stress at the apex. Second, it serves as a means of light and third is serves as an opening for the smoke from religious offerings.Pantheon is in use still as church. It is open for masses, in particular on Catholic days of obligation.

Getting there: The best way is to take a cab because there is no metro access.
There is no fee for entrance into the Pantheon