The hypogeum was an underground network of cages, rooms and passageways for people and animals below the Colosseum. It was here that gladiators and wild animals waited to face battle in the arena. Emperors often sponsored these battles as a way to win popularity with Romans and they were attended by thousands of spectators.
Today the Colosseum of Rome is the most visited monument in Italy and entrance lines can be very long. Here's how to buy Roman Colosseum tickets to avoid the lines. The hypogeum is usually closed to visitors but special tours are sometimes offered to view it. When you're in Rome, check to see if they are giving guided tours of the hypogeum for a fascinating look under the Colosseum.