Originally commissioned around 70 CE by the Flavian Emperor Vespasian, the Colosseum in Rome is the largest amphitheater ever built. But thanks to centuries of tourism, air pollution, and quick-fix repairs, the massive concrete-and-sand structure was looking pretty dingy. So in 2011, Conde Nast Traveler reports, Italian luxury leather brand Tod’s teamed up with Rome's Archaeological Heritage Department to restore the nearly 2000-year-old archaeological treasure to its former glory.

On Friday, July 1, the team celebrated a major milestone in the Colosseum’s extensive three-stage renovation process: the cleaning of 31 arches and 44,000 square feet of the structure's northern and southern façades. The current arch enclosure system also received brand-new gates. In all, the Colosseum’s exterior cleaning cost 6.5 million euros, or $7.2 million, the Associated Press reports

You can't just power-wash a historic monument, so, according to Wallpaper*, restoration workers had to take a photographic survey of the Colosseum and map its surfaces before using a special hydraulic spray to mist away dirt, deposits, algae, and moss by hand. The process took nearly three years—although amazingly enough, the Colosseum stayed open to tourists the entire time.

The entire Colosseum restoration project is costing Tod’s about 25 million euros overall. Eventually, the squeaky-clean building will also receive a new visitors center with a cafeteria, and its passageways and underground vaults will be restored. And by the end of 2018, the Colosseum might get a new floor—one that could allow performers to host entertainment events in one of Italy’s most majestic and storied venues.

But don’t expect the ancient wonder to be transformed into a performance stage just yet: Architects and engineers still need to figure out whether the building’s foundations can support a stage, and considering that the Colosseum's drainage system still uses ancient Roman pipes, its underground system would need a major upgrade.

[h/t Condé Nast Traveler]

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