The Colosseum's hidden underground has been closed to the public for 2,000 years - until now. See what it's like inside.

The Flavian Amphitheatre, commonly known as the Colosseum, which is one of Italy's most famous landmarks, was built under Emperor Vespasian.

Construction began in 72 AD, and it took nearly eight years to finish the arena, which would be the world's largest amphitheater for more than 450 years, according to Artnet News.

As the Colosseum's purpose shifted from an arena to a tourist attraction, the hypogea — or labyrinth of tunnels that were once below the stage — were closed off.

The Colosseum's 7 million annual visitors could gaze down into the hypogea without ever stepping foot into the area.

At a press conference on June 25, members of the media were able to walk through the hypogea, home to the previously unseen tunnels of the Colosseum, according to a Facebook post from the Colosseum Archaeological Park. The underground section has been open to the public since June 26.

The Colosseum held gladiator fights, hunts with wild animals, and even public executions, according to Artnet News.

The underground area served as the arena's backstage where gladiators and animals waited before heading into combat, according to CNN.

"This was the backstage of the shows that went on in the area. [It is the location for] all the preparation, even the technology -- they brought props, men and animals up into the area through a series of elevators and cargo lifts," Alfonsina Russo, director of the Colosseum Archaeological Park, told CNN.

By the 20th century, weather, natural disasters like earthquakes, and vandalism destroyed the majority of the original Colosseum, according to the History Channel.

The stage was also destroyed during the Colosseum's 2,000-year history, according to the History Channel. Without a stage, visitors were able to look down into the labyrinth of tunnels and hallways.

Nearly 525 feet of wooden walkways were installed into the hypogea, which allows visitors to walk where gladiators and animals awaited their battles, according to Artnet News.

According to Artnet News, restoring the hypogea was one part of a three-phase restoration project.

The $29.8 million project was funded by the Italian fashion company Tod's. In 2018, a team of experts began restoring the hypogea, Artnet News reports.

According to CNN, to restore the area, a team of archaeologists, geologists, restorers, engineers, and architects used photographic surveys and surface mapping.

"Each stone here is a witness of everything that occurred under the great arena of the Colosseum, from its inauguration in AD 80 to its final performance in AD 523," Alfonsina Russo, director of the Colosseum and its archaeological park, said in a press event, according to Artnet News.