The Colosseum hypogeum was the intricate network of tunnels, passageways, rooms and storage spaces beneath the floor of the main arena. Derived from the two Greek terms of hypo and gaia, it literally means “under the earth.” It was added to the Colosseum some years after its initial construction, by the Emperor Domitian. Its primary function was as a holding area for slaves and animals used in the gladiatorial games.
The Colosseum hypogeum was actually made up of two separate levels, with a remarkable amount of technical sophistication included in each. It was used for stage props and housed elaborate mechanical devices, used to move animal pens and slaves up to the main floor of the Colosseum.
This allowed for swift scenery changes through specially constructed vertical shafts and gave the master of ceremonies the option to customize each battle to his liking. Under the sand of the Colosseum’s substrate, thirty-six trap doors were hidden, making seamless transition between different battle scenarios possible.
Also, the hypogeum helped create special effects and surprise challenges for the contestants. For example, often a wild animal would be released through these openings in the midst of combat, to further add to the chaos. These animals would be penned, and a vertical winch known as a capstan would be used to raise their cage. A diagonal groove in the wall held a wooden ramp, which the beast would use to climb onto the Colosseum floor.
Some of the most talented engineers of the day worked to improve the Colosseum hypogeum constantly, and evidence points to a minimum of twelve separate improvement projects. This included the addition of a hegmata, which was a massive platform used to push large creatures such as elephants onto the main arena level. Although unseen by the Roman onlookers, the hypogeum was a true engineering marvel, which made the shows within the Colosseum an unrivaled spectacle.