"Pantheon"

The building is round in plan, except for the portico with large granite Corinthian columns (eight in the first rank and two groups of four behind) under a pediment. A rectangular vestibule links the porch to the rotunda, which is under a coffered concrete dome, with a central opening (oculus) to the sky. Almost two thousand years after it was built, the Pantheon's dome is still the world's largest unreinforced concrete dome.  The height to the oculus and the diameter of the interior circle are the same, 142 ft.

It is one of the best-preserved of all Ancient Roman buildings, in large part because it has been in continuous use throughout its history. The square in front of the Pantheon is called Piazza della Rotonda.

he Pantheon's large circular domed cella, with a conventional temple portico front, was unique in Roman architecture. Nevertheless, it became a standard exemplar when classical styles were revived, and has been copied many times by later architects