Photos: Italy's Colosseum underground labyrinth restored to eerie splendour

A view of the ancient Colosseum, in Rome. After 2-and-1/2 years of work to shore up the Colosseum’s underground passages, tourists will be able to go down and wander through part of what what had been the ancient arena’s “backstage.”

"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 hypogeum and inner walls of the Colosseum. The towering 2,000-year-old stone amphitheatre, the biggest in the Roman empire, is Italy's most popular tourist attraction, drawing 7.6 million visitors in 2019.

But its own beating heart, the underground passages, cages and rooms where prisoners, animals and gladiators waited to pass through trapdoors to enter the arena above their heads - itself long gone - only opened to the paying public on Friday after lengthy renovations.

The reopening to the public was announced Friday after meticulous restoration of the "hypogeum", or below ground area, with a new pathway offering intimate views and an app explaining the grisly details of the behind-the-scenes area.

A view of the newly restored lower level of the Colosseum. Once covered by a wooden floor, the maze of dark corridors and chambers served as the amphitheatre's backstage - and the last holding space for men and beasts who were released above to meet their fate.

Sponsored by Italian luxury shoe group Tod's, the restoration, begun in 2018.

More than 80 archaeologists, architects and engineers worked on the 15,000 sq metre "hypogeum" for two years to "bring back to the centre of the attention a monument that the whole world loves", according to Diego della Valle, chairman of Tods, the Italian fashion group that funded the work.

The circular balconies, long accessible to tourists, used to accommodate up to 70,000 spectators to watch gladiator fights, executions and animal hunts. The arena could also - before the hypogeum was built - be filled with water to re-enact sea battles.

"It is ... important for relevant companies to make themselves available to the country, understanding what they can do for the country," Della Valle said.

"This is about important pieces for Italy, monuments that are well-known all over the world, and tourism, which is not only entertainment but an important business in Italy which, if cared for properly, has no rival anywhere in the world," added Valle.

The Colosseum was first completed in 80 AD and the hypogeum constructed under Emperor Domitian.

The site was last used in 523 AD and the hypogeum was gradually covered by rubble until being dug out in the 19th century.

The labyrinthian system of passageways and chambers were key to the spectacles above ground, whether gladiator fights, hunts with wild African animals, or public executions.

It is the second part of a three-stage process that started eight years ago, with Tods pledging 25 million euros ($30 million) to pay for the project - one of a number of restorations of Italian landmarks funded by luxury goods firms.

The first phase of the makeover, including a cleanup of the facade, was unveiled in 2016. The final phase involves renewing the galleries and the lighting system and creating a new visitor centre. The project is set to be completed in about three years.