Rebuilt under Hadrian around 126 CE, the Pantheon’s unreinforced concrete dome (43.3 m span) with central oculus remains a marvel of material gradation and formwork. A temple turned church, it preserves bronze doors, marble revetments, and imperial scale. Modern care monitors cracking, rain ingress through the oculus, and crowd pressure in Rome’s historic core.
A granite‑columned pronaos leads to a circular cella perfectly proportioned: the height equals the diameter. The oculus (8.9 m) vents air and light; coffers reduce mass.
Aggregate gradation—travertine at the base to pumice near the crown—and stepped relieving arches lighten the dome. Timber centering once supported the pour; brick ribs articulate the drum.
Consecrated as Santa Maria ad Martyres in 609, the building’s continuous use aided survival. Baroque additions included altars and tombs (including Raphael).
Maintenance addresses joint loss in marble, patina on bronze, and drainage of the floor’s subtle slope. Visitor management limits echo and wear; sensors watch micro‑movements.
Rain through the oculus is part of the experience; visit early or late for calmer acoustics.
