A string of collapses at the nearby forum have also raised fears about visitor safety and whether the buildings can remain standing for much longer.
However the dire state of public finances in Italy, one of the most heavily indebted countries in Europe, means that funds are short and the government is having to turn to private investors to plug the 25 million euro ($32 million) gap.
“It’s a remarkable experiment,” said Francesco Giro, the undersecretary for Italy’s heritage ministry, which is running the tender with Rome’s city council.
“If all goes to plan, by 2013 the Colosseum will have been cleaned from top to bottom but even more important, it will be fully accessible to visitors,” he said.
The restoration project will see visitors offered multimedia tours of relatively unexplored areas, from the maze of underground chambers where the gladiators and wild animals were kept, to the uppermost terraces with their spectacular views.