The Pantheon is a magnificent ancient temple in Rome that was later converted into the church of Santa Maria ad Martyres. Dating from 125 AD, this is the most complete ancient building in Rome and one of the city's most spectacular sights.
The Pantheon was built on the exact site of two earlier Pantheon buildings, one commissioned by Marcus Vipsanius Agrippa (27-25 BCE) and the second by Domitian. The first was destroyed by fire in 80 CE and the second was struck by lightning in 110 CE and again burned down. The third Pantheon was probably begun in the reign of Trajan (98-117 CE) but not finally finished until around 125 CE when Hadrian was emperor. Following Hadrian’s usual practice of dedicating rebuilt buildings and monuments in honour of the original dedicator, the Pantheon is dedicated to Marcus Agrippa and the prominent inscription on the porch façade reads: M. AGRIPPA L.F. COS TERTIUM FECIT (Marcus Agrippa, son of Lucius, three-time consul, made this). Below the main inscription is a smaller one indicating the restorations carried out by Septimius Severus and Caracalla in 202 CE and reads: pantheum vetustate corruptum cum omni cultu restituerunt (with every refinement they restored the Pantheum, worn by age).
The interior of the dome was possibly intended to symbolize the arched vault of the heavens. The oculus at the dome's apex and the entry door are the only natural sources of light in the interior. Throughout the day, the light from the oculus moves around this space in a sort of reverse sundial effect. The oculus also serves as a cooling and ventilation method. During storms, a drainage system below the floor handles the rain that falls through the oculus. The dome features sunken panels, in five rings of 28. This evenly spaced layout was difficult to achieve and, it is presumed, had symbolic meaning, numerical, geometric, or lunar. In antiquity, the coffers may have contained bronze stars, rosettes, or other ornaments.