Pantheon is a building in Rome, Italy, commissioned by Marco Vipsanius Agrippa during the reign of Emperor Augustus (27 BC-14 AD) and rebuilt by Hadrian (117-118) around 126.
Its plant is circular with a portico of large granite Corinthian columns (eight in the first row and two groups of four in the second) supporting a pediment. A rectangular hall connects the portico to the rotunda, which is covered by a huge dome of concrete caissons surmounted by an open central opening (oculus). Almost two thousand years after it was built, this summit is still today the largest unreinforced concrete dome in the world. The height to the eyeglass and the diameter of the inner circumference are identical, 43.3 meters.
It is one of the best preserved ancient Roman structures and has remained in use throughout its history. Located in Piazza della Rotonda, the Pantheon has been used as a church, dedicated to “Santa Maria and the Martyrs” officially called Santa Maria dei Martiri (Latin: Sancta Maria ad Martyres) and informally of Santa Maria Rotonda since the 7th century. It is a smaller basilica of the Catholic Church and was a diaconia until 1929.