This is a photo of the Pantheon (adjective meaning "to every god"), a building in Rome, Italy, commissioned by Marcus Agrippa as a temple to all the gods of Ancient Rome, and rebuilt by Emperor Hadrian in about 126 AD. The nearly-contemporary writer (2nd-3rd c. AD), Cassius Dio, speculated that the name comes either from the statues of so many gods placed around this building, or else from the resemblance of the dome to the heavens.
The building is circular with a portico of three ranks of huge granite Corinthian columns (eight in the first rank and two groups of four behind) under a pediment opening into the rotunda, under a coffered, concrete, 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 (142 ft). A rectangular structure links the portico with the rotunda. It is one of the best preserved of all Roman buildings.