Pantheon

A temple with a huge unreinforced concrete dome with a central opening, allowing sun and rain to enter the building. Pantheon was commissioned by Marcus Agrippa as a temple to all the gods of Ancient Rome, and rebuilt later by Emperor Hadrian in about 126 AD. The building is circular with a portico of three ranks of huge granite Corinthian columns under a pediment opening into the rotunda, 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, 43.3 metres. A rectangular structure links the portico with the rotunda. It is one of the best preserved of all Roman buildings. It has been in continuous use throughout its history, and since the 7th century, the Pantheon has been used as a Roman Catholic church dedicated to "St. Mary and the Martyrs" but informally known as "Santa Maria Rotonda."