Pantheon, Rome

The Pantheon before you began as an ancient Roman temple and has served as the Catholic Basilica of Saint Mary and the Martyrs since the early seventh century. At the entrance, the portico gathers massive granite Corinthian columns beneath its pediment: eight stand across the front, with further rows set behind them. Beyond this formal threshold, the building opens into a circular rotunda beneath a coffered concrete dome.

Its oculus, the round opening at the crown, admits daylight directly into the interior. Agrippa commissioned an earlier sanctuary here during Augustus’s reign, but fires destroyed it; Hadrian completed the structure you see around the year one hundred and twenty-six. He deliberately retained Agrippa’s earlier dedicatory inscription, binding the rebuilt monument to its predecessor.

The dome remains the largest unreinforced-concrete dome on Earth, despite nearly two millennia of weather and use. Its interior diameter and the height from floor to oculus each measure forty-three metres, making the room feel like a perfect sphere imagined in stone and concrete. When the building became a church in the year six hundred and nine, that continuing religious role helped preserve it far more completely than many Roman monuments. The Pantheon is not a relic sealed away from the city; it is an ancient structure still living through its purpose.