ROME, July 31 (Reuters) - Rome's Colosseum might be leaning slightly but its stability is not in danger, said officials who on Tuesday announced that the ancient amphitheatre is about to undergo its first comprehensive restoration in 73 years.
An Italian newspaper reported at the weekend that the Colosseum, famous for hosting bloody gladiator fights in the days of the Roman Empire, was about 40 cm (16 inches) lower on the south side than on the north, suggesting it was in danger.
The Italian media described it as the "leaning tower of Pisa effect".
"There is no problem with its stability," Mariarosaria Barbera, Rome's archaeological superintendent, told a news conference.
"We are talking about a structure whose foundations are 13 meters (yards) deep. Roman constructions do not only stand up to centuries, they stand up to millennia," she said.
"We are monitoring it but there is no Tower of Pisa effect," Barbera said at the unveiling of the 25 million euro restoration project which will start in December and end in 2015.
The project, which had been delayed by three years of bureaucratic problems, will include the cleaning and restoration of the entire Colosseum, known in Roman times as the Flavian Amphitheatre.
It will be carried out in phases so that the Colosseum, which receives hundreds of thousands of visitors a year, will remain open. Only part of it will be covered by scaffolding at any one time.
"The monument is so big that there won't be too much inconvenience for visitors," Barbera said.
An underground visitors centre will be built under an adjacent piazza, freeing up more areas inside the monument, which are currently used as meeting points and ticket stalls.
Overall, some 25 percent more of the Colosseum will be open to visitors after the restoration, particularly the underground network of tunnels, storerooms and cages.
Two thirds of the underground parts are currently not open to the public.
Rome Mayor Gianni Alemanno said the traffic around the Colosseum will be re-routed by the end of the restoration to decrease damage from vibration. He said at a news conference it would be the first major restoration in 73 years.
"There have been various small projects but nothing of this level has been carried out in all this time," Alemanno said.
The work is being sponsored by Tod's, the luxury shoemaker and leather goods company.
Diego Della Valle, chairman of Tod's said the Colosseum had to be taken care of because "it does not only belong to Italians but to every citizen of the world." (Reporting By Philip Pullella, editing by Diana Abdallah)