The Arch of Constantine, a giant ancient Roman arch next to the Colosseum, was damaged after a violent storm hit Rome, conservation authorities said on Tuesday.
In a statement to Reuters, which first reported on the accident, the Colosseum Archaeological Park confirmed that the monument had been hit by lightning.
The triumphal arch was built in the fourth century A.D. to celebrate the victory of Constantine — the first Roman emperor to convert to Christianity — over his rival, Maxentius.
It is about 25 meters high and in the same pedestrian area where the Colosseum stands, a major tourist hotspot.
"A lightning strike hit the arch right here and then hit the corner, and we saw this fly off," a tourist told Reuters, pointing to a large block of stone on the ground.
Reuters video images showed other blocks of stone and rubble lying around the monument and archaeological park staff collecting them.
"All fragments were recovered and secured. Damage assessments have already begun and the analyses will continue tomorrow morning," the archaeological park said.
The arch was hit on its southern side, where conservation work had started two days ago and which will now also focus on repairing the damage, it said.
The accident took place during a heavy thunderstorm that felled trees and branches and flooded several streets of the Italian capital.
The Civil Protection agency said 60 millimeters of rain fell on central Rome in less than one hour, about as much as would normally fall in a month during autumn.
The freak weather was a so-called "downburst," Rome Mayor Roberto Gualtieri said, referring a severe storm featuring powerful downward winds, the kind believed to have caused the sinking of British tech tycoon Mike Lynch's yacht last month off Sicily.
"The event that hit Rome is truly unprecedented, because it was so powerful and concentrated in a very short time and in some areas of the city, starting from the historic center," Gualtieri said in a statement.
