The Colosseum you see today is really only half the story. For centuries the other half lay buried: the hypogeum, the elaborate underground complex that ran beneath the arena floor. Discovered by archaeologists in the nineteenth century and fully revealed in the twentieth, the hypogeum is one of the most extraordinary spaces in ancient Rome — and one of the least understood by the general public.
What the Hypogeum Is
The word hypogaeum comes from Greek: literally "that which lies beneath the earth." In the context of the Colosseum it refers to the network of galleries, corridors, cells and mechanical structures that occupied the entire surface beneath the arena floor — approximately 83 × 48 metres, an area comparable to a large palazzo.
This is not a single open space: it is a grid of two levels of corridors crossing at right angles, separated by perpendicular brick walls. Along these corridors were cells for animals, rooms for gladiators, storage for stage equipment, water tanks, and — most fascinating of all — a series of lifts and trapdoors that could hoist men, animals and scenery up onto the arena floor in a matter of seconds.
Construction: Domitian and the Finished System
The Colosseum was inaugurated in AD 80 under Titus, but the hypogeum as we know it did not yet exist at that point. Archaeological evidence and ancient sources suggest that the original arena floor was at ground level and that the space below was initially flooded for naumachiae — miniature naval battles.
It was Emperor Domitian (AD 81–96) who had the hypogeum built in its definitive form, probably during the 80s AD. The decision to excavate and structure the underground space ended the practice of naval battles inside the Colosseum (which moved to an artificial lake outside the city) and inaugurated the great era of exotic-animal hunts (venationes).
The construction required precision engineering: the perpendicular brick walls forming the hypogeum's grid also serve as foundations for the pillar system that supported the heavy wooden arena floor above.
The Structure: Corridors, Cells and Shafts
The Two Levels
The hypogeum is arranged on two superimposed levels. The lower level is the older and deeper of the two; the upper level was added or expanded at a later stage. The two levels communicated through openings in the ceilings and timber or stone staircases.
The main corridors run north–south and east–west, creating a grid that mirrors the symmetry of the amphitheatre above. The average corridor width is roughly 3–4 metres — wide enough for medium-sized animals (leopards, bears, deer); larger animals such as elephants or hippopotami required wider routes or alternative logistical solutions.
The Animal Cells
Dozens of rectangular brick-walled cells opened off the corridors. Some had wooden or iron grilles to contain the wild animals. Sizes vary: smaller cells for big cats and wolves, larger ones for bears and lions. Animals arrived at the hypogeum via lateral entrances that opened beneath the arches of the ground floor of the amphitheatre, connected to a network of access routes from outside.
The Gladiators' Rooms
Gladiators did not wait in the main hypogeum but in dedicated areas, partially separated from the animal zones for obvious safety reasons. Some of these spaces connected directly to the Ludus Magnus via the underground tunnel that linked the great gladiatorial school to the Colosseum — allowing fighters to reach the arena without crossing the streets of Rome.
Wells and Cisterns
The hypogeum was equipped with a network of wells and cisterns for water supply. Water was needed to give animals to drink, to clean the corridors after performances, and — according to some hypotheses — to flood the arena during the aquatic spectacles that preceded and followed Domitian's hypogeum era.
The Lift System: Engineering the Element of Surprise
The mechanical heart of the hypogeum was the lift system (pegmata), one of the most sophisticated applications of Roman engineering in the service of entertainment.
How They Worked
The lifts were counterweight-and-pulley devices that raised a wooden platform from hypogeum level up to the arena floor. At least 28 vertical shafts with the remains of lifting mechanisms have been identified along the hypogeum corridors. Each shaft was equipped with:
- Vertical timber or stone guides to stabilise the rising platform
- A rope or chain connected to a counterweight
- A release mechanism that opened the trapdoor in the arena floor at the right moment
The platform emerged through a trapdoor (horilegium) in the arena floor, disguised beneath sand or concealed by the arrangement of scenery. The mechanism was operated by workers (lorarii) in the hypogeum, probably enslaved specialists in charge of the machinery.
Load Capacity
Engineering reconstructions estimate that the platforms could lift loads of several hundred kilograms — enough for:
- A full-grown lion in its cage (180–250 kg)
- Three or four fully armoured gladiators
- Stage scenery elements such as artificial trees, built rocks, and complex sets
Ancient sources describe entire forests and landscapes that appeared to spring from nowhere on the arena floor — effects requiring precise coordination between dozens of lifts operated simultaneously.
Directing the Show
The editor muneris — the patron and commissioner of the games — was not just the financial backer: he was the director of a show requiring sophisticated underground stage management. We have accounts of spectacles in which dozens of animals emerged simultaneously from different points across the arena, creating total surprise for the crowd. This required a signals system — probably acoustic, given the darkness and noise of the hypogeum — to coordinate the workers at each lift.
The Animals of the Hypogeum: Logistics of an Imperial Zoo
Managing animals in the Colosseum's hypogeum was a logistical undertaking of enormous complexity — comparable in scale to running a large modern zoo, with the added challenge that every animal had been transported from across the Empire.
Where They Came From
The animals used in venationes came from every corner of the Roman world and beyond:
- North Africa: lions, leopards, panthers, cheetahs, ostriches, crocodiles, hippopotami, rhinoceroses
- Asia: tigers (from Mesopotamia and India), bears, monkeys
- Northern Europe: Germanic forest bears, deer, wild boar
- East Africa: elephants, zebras, giraffes (which the Romans called camelopardalis)
Transport took months: specialised cages, adapted ships, veterinary support staff. On arrival in Rome, animals were held in designated facilities (vivaria) near the city before being transferred to the hypogeum in the hours preceding the shows.
The Problem of Large Animals
Elephants and giraffes could not pass through the standard hypogeum corridors. Solutions included special ground-level entrances with ramps, or — for the grand venationes of the Augustan era and earlier — direct entry into the arena from outside through the large carriage gates still visible today at either end of the major axis.
The Numbers
Ancient sources record staggering figures for animals killed during the games. For the Colosseum's inauguration alone in AD 80, 9,000 animals were reportedly killed over one hundred days. Trajan celebrated his Dacian conquests with games involving 11,000 animals over 123 days. These numbers left ecological traces: some North African populations of large felids were probably driven toward local extinction by the Roman games industry's demand.
Discovery and Excavation
Medieval Oblivion
After the end of the spectacles — traditionally placed in AD 523 for venationes and AD 404 for gladiatorial munera — the Colosseum was progressively abandoned and then quarried for building materials. The wooden arena floor rotted and collapsed, exposing the hypogeum below. Through the Middle Ages and the Renaissance, the hypogeum was visible but ignored: it was used as a rubbish dump, a storage space, or simply filled with debris over time.
Nineteenth-Century Excavations
The first systematic excavations of the hypogeum began in the second half of the nineteenth century, running in parallel with the Romantic era's great enthusiasm for classical archaeology. Work by Francesco Gori and later by Giacomo Boni uncovered the main corridors and the lift mechanism structures, but without a full understanding of how the system functioned.
Twentieth- and Twenty-First-Century Research
The modern understanding of the hypogeum is the result of excavation and study campaigns developed from the 1970s onward, with a decisive turning point in the 2000s when restoration funded by the Tod's fashion group allowed the entire complex to be cleaned, consolidated and systematically studied.
Archaeological research included:
- Analysis of organic residues to identify which animal species were present
- Three-dimensional reconstruction of the lift system
- Complete mapping of the corridors and identification of each space's function
- Study of depositional layers to reconstruct the chronological sequence of building phases
Visiting the Hypogeum Today
The Colosseum hypogeum is not accessible with a standard ticket. To visit it you need the Full Experience ticket (or equivalent), which includes:
Tickets and Access
| Ticket Type | Price | Hypogeum Included? |
|---|---|---|
| Standard | €18 | No |
| Full Experience | €22 | Yes |
| Under-18 EU | Free | No (standard only) |
| First Sunday of the month | Free | No |
The hypogeum route is accessible only on guided tours at set times, with limited group sizes to protect the fragile underground environment. Online booking is strongly recommended, especially during high season (April–October).
What You See
The guided hypogeum tour allows visitors to:
- Walk along the main corridors (approximately 300 metres of route)
- See the animal cells with the remains of the grilles
- Examine the lift shafts and hoisting mechanisms
- Observe from inside the supporting structure that held up the arena
- Look upward through the trapdoors still visible in the floor above
The temperature in the hypogeum is noticeably lower than in the arena: in summer it is 5–8°C cooler, making a visit pleasant even on the hottest days. A light extra layer is still a good idea.
Photography
The hypogeum is one of Rome's most photogenic spaces, with its corridor perspectives receding into shadow and columns of light dropping through trapdoors from above. Tripods are not permitted; flash is inadvisable on ancient walls. A camera or smartphone with good low-light performance produces the best results.
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Frequently Asked Questions
Can you visit the hypogeum without a guide? No. Access to the hypogeum is permitted only as part of guided tours at set times, for reasons of safety and conservation.
How long does the guided hypogeum tour take? The full Full Experience visit (arena + hypogeum + belvedere) lasts approximately 2–2.5 hours. The hypogeum portion alone takes 45–60 minutes.
Is the hypogeum accessible for disabled visitors? Partially. Some sections of the route have steps and uneven paving. The Colosseum provides an alternative accessible route; it is recommended to contact the ticket office in advance to plan the visit.
How deep is the hypogeum? The lower hypogeum level is approximately 6 metres below the original arena level and around 9 metres below the external street level of the ancient Via Nova/Via Sacra.
Have organic materials been preserved in the hypogeum? Yes. Excavations have yielded fragments of charred timber (from the lift structures), animal bones, remnants of ropes and leather, pottery fragments, and coins. The relatively stable underground climate contributed to the preservation of these materials.
What recent changes have been made to the hypogeum? As part of the project to install the new Colosseum arena floor (inaugurated experimentally in 2023), additional studies were carried out on the hypogeum to verify the new floor's compatibility with the ancient underground structures.
Article No. 4 — TIER S — MON-01 Colosseum Type: HISTORY Words: ~2,600