The Italian government has announced it will accept a private donation to restore the Colosseum. Work is to begin in December.
Tod's, a luxury shoemaker, is providing 25 million euros ($US31 million) for the work, which will last 2½ years. The site will remain open to visitors.
There has long been concern that the ruin is being damaged by vibrations and pollution. On Sunday, it was reported that the building is tilting about 40cm to one side.
Built 2000 years ago, the Colosseum was the biggest amphitheatre in the Roman Empire.
Rome's superintendent for archaeological heritage, Mariarosaria Barbera, said that the restoration would make 25% more of the Colosseum accessible to visitors in the future.
The building will be cleaned and restorers will also repair cracks and remove temporary metal arches installed on the ground level.
A new visitor centre will also be built outside the ruin.