Rome Coliseum site features

The Colosseum is an ellipse, not a circle, and the moment you walk along it the difference shows. The plan is 189 metres long and 156 metres wide over a base of 24,000 square metres, so the curve never closes the way a round building's does — the far side keeps sliding away as you move.

The surviving north wall gives you the full original height: 48 metres. Four storeys of arcade, one stacked on the next, with the perimeter once running 545 metres around. Where that outer ring has gone the building drops abruptly to its inner structure, and the join is the most obvious thing about it from the street.

The stonework is pitted all over with small rectangular holes, and they are not decay. The outer wall took over 100,000 cubic metres of travertine set without mortar, held together instead by 300 tons of iron clamps. The clamps were dug out for their metal; the holes are where they sat.

Two blunt brick triangles brace the ends, and they are modern. The facade was reinforced with triangular brick wedges in 1807 and 1827 — plain, steeply raking masses against the Roman arcading, impossible to mistake for it once you know.

At ground level the entrances are numbered, in Roman numerals, cut into the stone. There were eighty, of which 76 were for ordinary spectators; much of the outer ring is gone, but entrances XXIII to LIIII survive and you can read them as you pass.

Inside, the floor is missing and that is the point of the view. The arena was an ellipse 87 metres long and 55 wide, ringed by a wall 5 metres high; what you look down into instead is the brick labyrinth beneath it, partly excavated in 1810–1814 and 1874 and fully exposed in the 1930s. The passages carried animals and gladiators up to the floor that is no longer there.

The seating survives as slope rather than as seats. Rising banks of broken concrete and brick run up from the arena wall, with the vaulted spaces beneath them open — the same vaults that were converted into housing and workshops and were still being rented out as late as the twelfth century.

Look closely at the stonework and some of it has been written on. The names of some fifth-century senators are still carved there, presumably marking areas kept for their use.

Outside, five tall stone posts stand clear of the building on the eastern side. They are the remnant of a ring that once ran round the whole perimeter at a distance of 18 metres — explained variously as a religious boundary, an outer line for ticket checks, or anchors for the awning.

And it is greener than photographs suggest. 242 plant species are counted on it today, out of 684 identified since 1643; an eradication attempt in 1871 cleared much of it and most of it came back.

The hypogeum

Two levels of tunnels, animal cages and lift shafts under the arena, opened to the public in summer 2010. This is the part that explains the spectacle mechanically rather than rhetorically: the floor was a stage with machinery under it, and the machinery is what survives.

The upper levels

Open for guided visits since 2017, and the only place to get the view down the long axis from where most of the audience actually sat. Access is by guided tour rather than general admission.

The Commodus Passage

The route by which emperors entered discreetly, and the site of a failed assassination attempt on Commodus. It was rediscovered in the 1810s, restored between October 2024 and September 2025 with its decorative stuccoes recovered and a walkway added, and opened to the public on 27 October 2025. A further restoration project is planned to begin in 2026, so check what is accessible for your date.

The numbered arches

Entrances XXIII to LIIII on the surviving outer wall, with the Roman numerals still legible. Free to look at, and the clearest surviving evidence anywhere of how a Roman crowd was sorted and routed.

The senators' graffiti

Names of fifth-century senators carved into the stonework, reserving their seats. Five centuries after the building opened, people were still marking their places in it.

The Ludus Magnus

The gladiator school east of the amphitheatre, visible from street level and free, with its own small training arena and the underground passage that connected it to the Colosseum.