28/09/2026
🏛️ 2,000 years old, and its concrete dome is still the largest unreinforced one on Earth.
This is the Pantheon in Rome, built under Emperor Hadrian around 126 AD (the inscription up front actually credits Marcus Agrippa, from an earlier temple on the same site). At its center sits the oculus — a 30-foot open hole in the dome's ceiling, the only source of light inside, rain and all.
No modern engineer has replicated its concrete formula. The Romans mixed volcanic ash into the concrete and made it progressively lighter toward the top, a trick that's kept this dome standing through two millennia of earthquakes, wars, and empires rising and falling around it.
It's outlasted the very religion it was built for — a pagan temple to "all the gods," now a functioning Catholic church.
👉 What ancient technology do you wish we still had today? Comment below. 👇