Work on the still-in-use Cloaca Maxima, or "Giant Sewer," mentioned in the works of the ancient historian Livy and believed to be built in the fifth century B.C. before Rome became a republic, began Wednesday, The Daily Telegraph reported.
The British newspaper said decades of inadequate maintenance have left the giant sewer clogged with debris and silt, and vulnerable to blockage and collapse.
"We will free the drain of detritus and sediment. We still need to get funding so we will proceed bit by bit, but the hope is to complete the work within two years," cultural heritage official Elisabetta Bianchi told the Italian newspaper La Repubblica.
Flooding in Rome last year revealed cracks and other inadequacies of the sewer, said architect Maria Grazia Filetici of Rome's cultural heritage office.
Officials said the Cloaca Maxima, originally dug as a canal but later covered over to become a subterranean sewer, is filled with huge quantities of rubbish, including plastic bags and tangled electric cable.