Discover Rome Coliseum

The Colosseum is the largest amphitheatre ever built, and the reason it looks half-destroyed is geological rather than historical. It stands on flat, partly alluvial ground where a lake in Nero's palace grounds had been, so it had to carry its own slope in vaults instead of resting on a hillside — and in 1349 an earthquake brought down the outer south side, the side sitting on the less stable terrain. The north arc of the outer wall still stands. What most visitors photograph is a building with one façade and one cross-section.

Begun under Vespasian around 70–72 A.D. and inaugurated under Titus in 80, it is elliptical, 189 metres long and 156 metres wide, with an outer wall 48 metres high and a perimeter that originally ran 545 metres. Modern estimates put capacity at around 50,000; the Codex-Calendar of 354 claimed 87,000.

Three things opened to visitors within living memory and change what a ticket can now include: the hypogeum, the tunnel network under the arena floor, opened in summer 2010; the top two levels have been open for guided visits since 2017; and the Commodus Passage, the emperors' private entrance, opened on 27 October 2025 after a year of restoration.

The Colosseum is the largest amphitheatre ever built, and the reason it looks half-destroyed is geological rather than historical. It stands on flat, partly alluvial ground where a lake in Nero's palace grounds had been, so it had to carry its own slope in vaults instead of resting on a hillside — and in 1349 an earthquake brought down the outer south side, the side sitting on the less stable terrain. The north arc of the outer wall still stands. What most visitors photograph is a building with one façade and one cross-section.

Begun under Vespasian around 70–72 A.D. and inaugurated under Titus in 80, it is elliptical, 189 metres long and 156 metres wide, with an outer wall 48 metres high and a perimeter that originally ran 545 metres. Modern estimates put capacity at around 50,000; the Codex-Calendar of 354 claimed 87,000.

Three things opened to visitors within living memory and change what a ticket can now include: the hypogeum, the tunnel network under the arena floor, opened in summer 2010; the top two levels have been open for guided visits since 2017; and the Commodus Passage, the emperors' private entrance, opened on 27 October 2025 after a year of restoration.

The Colosseum is an elliptical amphitheatre of travertine, tuff and brick-faced concrete, 189 metres long, 156 metres wide, 48 metres to the top of the outer wall, with a base area of 24,000 square metres. The arena inside is an ellipse of about 87 by 55 metres, ringed by a wall five metres high with the seating tiers rising behind it.

The outer wall is the part worth reading closely. It required over 100,000 cubic metres of travertine, set without mortar and held together by some 300 tons of iron clamps — and the holes pocking the surviving stonework are where those clamps were later dug out for their metal. Only the north arc still stands; the triangular brick wedges closing it at each end are nineteenth-century buttresses, not Roman work.

Eighty arched entrances ringed the ground floor, 76 for ordinary spectators, each numbered so a ticket could direct its holder to a specific stair. The surviving stretch carries entrances XXIII to LIIII, and the numerals are still legible above the arches. Inside, the names of some fifth-century senators remain carved into the stonework, apparently reserving their places.

Around the outside, 18 metres from the wall, stood a ring of tall stone posts; five survive on the eastern side. What they were for is genuinely unsettled — a religious boundary, an outer line for ticket checks, or anchors for the velarium, the awning.

The Colosseum had to build its own hill. A Greek theatre is cut into a slope. An amphitheatre on flat ground has no slope to cut, so the seating is carried on rings of arcaded piers with radial barrel vaults springing between them and stepping upward. That system is what produces the corridors, stairs and vaulted chambers a visitor walks through: they are not rooms added to the building, they are the space left over inside its structure.

The ground was the problem. The site was the valley of a lake in Nero's palace grounds — drained, densely inhabited before the Great Fire of 64, and partly alluvial. The whole southern arc sits on that softer material, which is why the 1349 earthquake took down the south side and left the north standing. The building did not fail; the ground under half of it did.

Travertine without mortar. The outer order used over 100,000 cubic metres of travertine laid dry, its blocks tied by roughly 300 tons of iron clamps. It is an efficient system and a vulnerable one: iron is worth money, and once the clamps were being dug out the wall was being taken apart whether or not anyone intended to demolish it.

Below the floor. The hypogeum is two levels of tunnels, cages and lift shafts that delivered animals and fighters to the arena from underneath. It was partly excavated in 1810–1814 and 1874 and fully exposed in the 1930s, which is why the building now has no floor: what you look down into was designed never to be seen.

And an industry around it. The Ludus Magnus, the gladiators' training school with its own miniature arena, stood immediately east and was joined to the amphitheatre by an underground passage. Nearby were the Ludus Matutinus for animal fighters, the Armamentarium for weapons, the Summum Choragium for machinery, the Sanitarium for the wounded and the Spoliarium for the dead.

Why does it look half-destroyed? The earthquake of 1349 brought down the outer south side, which stood on less stable alluvial ground. The north arc survived. The fallen travertine was then quarried for Roman building for centuries, so the damage was geological first and economic afterwards.

Were Christians martyred here? The tradition says so; the medieval evidence does not support it. The Colosseum is not in the pilgrim itineraries, and the twelfth-century Mirabilia Urbis Romae places the martyrdoms at the Circus Flaminius instead. The association grew from the sixteenth century onward and was endorsed by Benedict XIV in 1749 — which is precisely why the building was saved.

How many people did it hold? Modern estimates put it around 50,000. The Codex-Calendar of 354 claims 87,000. Take the range rather than either figure.

Is the arena floor original? No — there is no floor. What you look down into is the hypogeum, the tunnel network beneath it, partly excavated from 1810 and fully exposed in the 1930s. A partial modern platform covers a section of it.

What are the holes all over the stonework? Sockets where iron clamps were dug out. The outer travertine was laid without mortar and tied with roughly 300 tons of iron; the metal was worth removing.

Do I need a separate ticket for the underground or the upper levels? Generally yes. The hypogeum, the top two levels and the Commodus Passage are additional guided visits rather than parts of general admission, and they sell out first. Choose before booking.

Is the Colosseum older than the Arena di Verona? No — Verona's is roughly forty years older. The instructive difference is what came next: Verona kept repairing and using its amphitheatre, while this one was quarried and became a ruin.