The beating heart of Rome is not the marble of the Senate, it's the sand of the Colosseum, the Roman senator Gracchus said in the 2000 Oscar-winning movie Gladiator. The Colosseum is an ancient structure built more than 2000 years ago. The Romans used the huge, rounded building as a performance space. Thousands of people could be seated in the open-air theater to watch a show or public activity. Performances included competitions by professional fighters, called gladiators, most of whom were enslaved. They often fought other gladiators but also could face prisoners or dangerous animals, like lions. Executions also took place there. The Colosseum is the largest building that the Roman Empire produced. It is also Italy's most popular ancient structure. More than 7.6 million people visited the Colosseum in 2019. But its own beating heart is the underground passages and rooms where prisoners, animals and gladiators waited to enter the field above their heads. Now, that underground area, known as the hypogeum, is open to the public after lengthy repairs. More than 80 archaeologists, architects and engineers worked on the 15,000 square-meter area for two years. Tod’s, the Italian clothing company, supported the work. Its chairman, Diego Della Valle said the effort aimed to "bring back to the center of the attention a monument that the whole world loves." The theater’s balconies used to hold up to 70,000 people who would come to watch the gladiator fights, executions and animal hunts. Before the hypogeum was built, the space could also be filled with water to re-enact sea battles. Now a new 160 meter walkway permits visitors to see the hypogeum. It is the second part of a three-part process that started eight years ago, with Tod’s promise of $30 million to pay for the project. Tod’s is also supporting several similar projects in the country.