Pantheon

The Pantheon in Rome is the best-preserved building of ancient Rome, a former temple to all the gods rebuilt by Emperor Hadrian around 125 AD on the site of an earlier structure commissioned by Marcus Agrippa in 27 BC — whose name remains inscribed on the pediment. In 609 AD it was consecrated as a Christian church (Santa Maria ad Martyres), a status that protected it from the dismantling that destroyed most other Roman buildings. The defining architectural achievement is the dome: at 43.3 metres in diameter, it remained the world's largest dome for 1,300 years and still stands as the largest unreinforced concrete dome ever built. The coffers — sunken panels in the dome's interior — decrease in size toward the oculus, the 9-metre open eye at the apex, which is the building's only source of natural light and the point through which rain falls directly onto the sloped, drain-equipped floor. At noon on April 21 — Rome's traditional founding date — sunlight falls precisely through the oculus and illuminates the entrance. The interior diameter equals the interior height (43.3 metres each), forming a perfect sphere that would exactly contain a sphere of that radius. The tombs of Raphael (d. 1520), King Vittorio Emanuele II, and King Umberto I are set into the perimeter walls. Entry now requires a pre-booked timed-entry ticket available from the official site; the building became an official museum site in 2023 with paid admission after centuries of free entry.