Throwback: The world’s oldest monolithic dome — the Pantheon

The entrance to the Pantheon in Rome, Italy.

The Romans built The Pantheon in 126 A.D. as a “temple to all gods.” The columned portico, triangular pediment, and large, domed rotunda became the design template for important landmarks worldwide.

Jfabrix101 / Wikimedia Commons / CC BY-SA 4.0

The unreinforced concrete dome is the largest in the world.

The dome — 20 feet thick at the base, tapering to 7.5 feet thick at the oculus — is the largest unreinforced concrete dome in the world. This engineering marvel caps a 142-foot diameter rotunda with a perfect hemisphere.

Bjørn Christian Tørrissen / Wikimedia Commons / CC BY-SA 3.0

The Pantheon is arguably the first monolithic dome. Not in the sense of the modern, insulated structure, but as the original one-piece, monolithic, concrete dome — the largest unreinforced concrete dome in the world. No other significant structure of antiquity has survived as well preserved nor with the roof intact. More than that, it’s still in use today and visited by millions annually.

Constructed in Rome, Italy, around 126 A.D., this single structure changed architecture forever. According to John Ochsendorf, Professor of Architecture and Civil & Environmental Engineering at MIT, “The Pantheon is the creation and invention of the dome in Western architecture.”

It is the blueprint for renaissance churches, university structures, and capitol buildings. “You put a large dome, perhaps grand columns in front, and that says this is a seriously important building,” said Ochsendorf. “But what it also says is we are aware of the Pantheon, and you should be, too.”

Michelangelo called it “angelic” and “not human.”

We call it a testament to the strength, longevity, and beauty of the dome. In today’s throwback, we revisit The Pantheon — A temple to all gods our original story about the Pantheon, updated with new photographs and a beautiful video by CNN Style.

A fisheye view inside the Pantheon of the rotunda, dome, and oculus.

The 30-foot diameter oculus at the dome apex overlooks the spectacular rotunda. Priceless works of art and statues line the perimeter. Nine million people visited the Pantheon in 2019 making it the most popular historical site in Italy.

Victor Grigas / Wikimedia Commons / CC BY-SA 4.0