The Pantheon (/ˈpænθiən/ or US /ˈpænθiɒn/;[1] Latin: Pantheon,[nb 1] from Greek Πάνθειον Pantheion meaning "[temple] of every god") is a building in Rome, Italy, on the site of an earlier building commissioned by Marcus Agrippa during the reign of Augustus (27 BC – 14 AD). The present building was completed by the emperor Hadrian and probably dedicated about 126 AD. He retained Agrippa's original inscription, which has confused its date of construction.[2]

The building is circular with a portico of 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.[3] The height to the oculus and the diameter of the interior circle are the same, 43.3 metres (142 ft).[4]

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, and since the 7th century, the Pantheon has been used as a church dedicated to "St. Mary and the Martyrs" (Latin: Santa Maria ad Martyres) but informally known as "Santa Maria Rotonda".[5] The square in front of the Pantheon is called Piazza della Rotonda. The Pantheon is a state property, ruled by Italy's Ministry of Cultural Heritage and Activities and Tourism through the Polo Museale del Lazio; in 2013 it was visited by over 6 million people.