The Colosseum has emerged more imposing than ever after a multimillion-euro cleaning operation.

The restoration work saw a patina of soot and grime removed from the ancient arena, which has been affected by pollution in traffic-clogged Rome for decades.

Footing the bill is shoe and luxury goods maker Tod's, after company founder Diego Della Valle responded to a government call to the private sector to help Italy care for its immense art and archaeological treasures.

Buoyed by the brighter look of the Colosseum, Italy's culture minister Dario Franceschini announced on Friday that €18 million have been found to replace, by the end of 2018, the arena's long-vanished floor with one that could support modern-day entertainment - although monument-rocking concerts have been ruled out.

The stage would be used for "cultural events of the highest level", Mr Franceschini said.

The first stage of the restoration consisted of gently removing the effect of pollution on the exterior of the monument - which dates from the first century - with water misters and brushes wielded by hand.

The monument stayed open to tourists during the nearly three-year-long restoration of the outside, with scaffolding covering only one section at a time.

The exterior cleaning cost €6.5 million.

Tod's is paying €25 million for the entire project, whose next steps include constructing a visitors' centre with a cafeteria and shoring up the bottom, where wild beasts and scenery were kept for spectacles for the ancient Roman masses.

Mr Della Valle received effusive thanks from Italy's prime minister Matteo Renzi on Friday.

Companies ranging from Italian fashion houses to a mattress manufacturer to a Japanese textile maker have paid for restorations including the Trevi Fountain, the Spanish Steps and Rome's own Pyramid.

Mr Franceschini pointed out that the shoe magnate was especially generous, since Mr Della Valle offered the funds before a new Italian law took effect in late 2014, giving modern-day versions of Medici princes of the arts huge tax breaks.

Under that new strategy, more than €100 million have been donated, Mr Franceschini said.

Architect Gisella Capponi, who directed the restoration, said the cleaning allows the Colosseum's creamy hues of travertine stone to be appreciated again.

"The coloration highlights the monument" while the dirt and grime "gave an image of being more a ruin than it really is", she said.

The stone had been so blackened that the Colosseum almost seemed to fade into the background for Romans who passed it daily on their commutes.

But now "the effect is one of surprise", Colosseum director Rossella Rea said.

Besides Mr Della Valle's generosity, the Colosseum benefitted from a city ordinance forbidding private cars on the nearby boulevard, which flanks Roman and Imperial Forums.

Taxis and buses, but not private cars, are allowed on weekdays. On weekends, only pedestrians and cyclists can use the boulevards.

Shopkeepers and other businesses in the area have complained bitterly about the traffic ban but Ms Rea is unrepentant about the need to protect the arena, a Unesco World Heritage site that is considered Italy's most famous icon.

"If the heavy traffic, which did the damage, returns, all you'll need is three, four years to coat the Colosseum again in soot," she said.

To keep its clean look, all the monument will need in the next years is an annual check-up, with workers going up in cherry-pickers to remove weeds.