The Pantheon in Rome was completed under Emperor Hadrian around 125 CE.
The building is famous for its vast concrete dome and central opening, the oculus. The oculus is about 8.7 meters wide and remains the Pantheon’s only major source of direct natural light. Rain can enter through it, but the slightly convex floor and drainage holes help carry water away.
Hadrian’s Pantheon replaced an earlier temple commissioned by Marcus Agrippa, whose inscription—“M·AGRIPPA·L·F·COS·TERTIVM·FECIT”—was retained on the façade. The present structure is generally dated to Hadrian’s reign, although its exact completion year is not recorded. The name comes from Greek roots meaning “all the gods.”
The Pantheon survived because it was converted into a Christian church in the seventh century, becoming Santa Maria ad Martyres. Its dome influenced later architecture, including Renaissance buildings. Raphael is buried inside, as are several Italian kings.