Several vandals from a climate activist group called Ultima Generazione dyed the water in Rome's Trevi Fountain black Sunday before police hauled them away, multiple outlets reported.
"Enough of these absurd attacks on our artistic heritage," Rome's mayor Roberto Gualtieri tweeted, adding that restoration would be "expensive and complex."
He asked that activists stop putting monuments at risk.
Gualtieri praised the timely intervention of the local police, thanking them for ensuring the damage was kept to a minimum. The mayor said the vandalism would require wasting 300,000 liters of water.
Later in the day, the mayor shared a video on Twitter showing the fountain apparently returned to its original condition. In the video, tourists are heard cheering as clear water begins flowing from marble marvel.
"Now [the fountain] can go back to enchant the world," the mayor wrote.
The climate protesters held banners that said "we won't pay for fossil fuels" and shouted about the country "dying," according to Reuters. The banners, which appear to have been professionally printed, were orange with white lettering.
The vandals claimed they used "vegetable charcoal" to darken the waters of one of the Eternal City's most popular tourist attractions.
In a Twitter post, the group said one in four houses in Italy are vulnerable to floods and asked how much longer they had to wait before government took concrete action.
Tradition dictates that visitors turn their back to the fountain and toss a coin into the water over their left shoulder in the hopes they will return to Rome again in the future. A second coin is said to promise love, and a third is to guarantee marriage, TripSavvy explains.
Coins thrown into the fountain are donated to charity.
The 18th century marble fountain commissioned by Pope Clement XII is about 85 feet high and 160 feet wide. Nicola Salvi began its creation in 1732 and it was completed by Giovanni Pannini in 1751 following Salvi's death.
Watch video below of climate vandals dying the water of Rome's 18th century Trevi Fountain black with charcoal.
Like Blaze News? Bypass the censors, sign up for our newsletters, and get stories like this direct to your inbox. Sign up here!