What is under the Colosseum

The hole in the middle of the Colosseum is the part everyone photographs and almost nobody can read. It is not a basement and not a ruin of one: it is the stage machinery, and the building above it was the auditorium.

A machine, not a cellar

Under the arena run two levels of parallel corridors, crossed by radial ones: a grid of brick walls that carried the wooden floor and everything needed to get a spectacle onto it. Cages, ramps, store rooms, drainage channels. What survives is the stonework of a stage cellar whose wooden parts have all gone.

The floor itself was planking laid over those walls and covered in sand — harena, which is where the word arena comes from. The sand was not decoration. It absorbed blood and could be raked over between events.

The lifts

Set into the corridors were shafts for hoists — around thirty of them, worked from below by capstans and counterweights, each opening onto a trapdoor in the floor. An animal went into a cage at the bottom, several men turned the winch, and the cage rose into daylight in the middle of the show.

This is the point of the whole apparatus: nothing was supposed to walk in through a door. Things appeared. A building designed so that a leopard could arrive from beneath the sand, on cue, in front of fifty thousand people, is a piece of theatre engineering, and the ruined corridors are its remains.

It was not there on opening day

The amphitheatre was inaugurated under Titus in AD 80 with a hundred days of games. The underground as you see it belongs to the next reign, Domitian’s: it was dug out and built up afterwards, which is why the corridors cut into the original arena level rather than sitting under it neatly.

Before it existed, sources describe water shows in the arena. Whether the building was ever genuinely flooded for a mock naval battle, and how, is still argued over: the drains are there, the accounts are there, the engineering is disputed. The hypogeum settled the question in any case — once it was built, flooding was impossible.

The tunnel to the gladiator school

Passages led out of the underground beyond the walls of the amphitheatre. One connected to the Ludus Magnus, the training school just to the east, whose excavated courtyard — a small practice arena with its own tiers — is visible from the street today, sunk below the modern pavement. Gladiators came to work without ever crossing the square.

What you can see today

Part of the arena has been re-decked, so a strip of the building reads as it once did, and the rest is left open so the corridors below stay visible. Walking those corridors requires the ticket that says so, in limited, accompanied groups.

The odd truth is that the hypogeum is easier to understand from above. From the stands the whole plan lies open like a cutaway drawing: the long central spine, the parallel corridors on either side, the square shafts where the lifts stood. Down inside it, you see brick walls higher than your head and lose the shape entirely.

What to look for from the stands

• the central corridor running the long axis of the oval — the service spine of the whole floor
• the regular square recesses in the walls: sockets for the timbers of the hoists
• the difference in brickwork between levels, where the building was repaired, reused and rebuilt over four centuries of use
• the drains at the lowest level, which had to keep a hole in the middle of Rome dry
• the gates at the two ends of the long axis: one for the entry procession, one through which the dead were carried out

Updated 2026-09-11