The Pantheon
A Roman temple under the largest unreinforced concrete dome in the world.
The Pantheon in Rome was finished around 125 CE, under the emperor Hadrian. Nearly 1,900 years later, its dome is still the largest ever built of concrete with no steel inside.
Inside, the dome is as wide as it is tall, 43.3 metres both ways, so a whole sphere would fit in the room. The only window is the oculus, a round opening at the top about 8 metres across. Rain falls straight through it, onto a floor built to drain.
In Forever Wonder it arrived early. The town is still in the Bronze Age, more than a thousand years before the Romans built the real one.
Ever wonder?
How has a concrete dome stood for almost 1,900 years with no steel inside?
The Romans made the concrete lighter the higher it goes, mixing in light volcanic stone near the top, and cut square coffers into the ceiling to take weight away. The ring round the oculus is squeezed from every side, which holds the top together.
Facts
- Finished
- About 125 CE
- Dome
- 43.3 m across
- Oculus
- About 8 m wide
- Columns
- 16, granite from Egypt