Colosseum history
Three emperors built it across three decades, and the space you can now walk underground was the last major addition.
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Walk through the hypogeum Domitian added on the underground tour.
See the underground tour
Photo: BeBo86, CC BY-SA 3.0, via Wikimedia Commons.
Construction
Emperor Vespasian began construction between 70 and 72 CE. It was funded with plunder from the sack of Jerusalem in 70 CE and built largely by enslaved Judaean labourers. Vespasian died before it was finished. His son Titus dedicated the completed amphitheatre in 80 CE with 100 days of games, including gladiatorial combat and staged animal hunts.
The building was not quite finished at that dedication. Titus's brother Domitian added the fourth story and the hypogeum, the network of underground chambers and tunnels used to stage the animals and fighters entering the arena above. That same space is what you walk through today on the underground tour.
Checked 2026-09-28 · source: Britannica, History.com, cross-checked
Scale
The amphitheatre held an estimated 50,000 to 80,000 spectators, entered through 80 ground-level arches, 76 for the public and 4 reserved for ceremonial and elite use. It remains the largest amphitheatre ever built.