The Telegraph seems to be one of the only newspapers mentioning this … the salient excerpts:
Severe flooding led to tourists being shut out of the 2,000-year-old Roman amphitheatre as well as the nearby Roman Forum and Palatine Hill, and the ancient Roman port of Ostia, west of the capital.
The Colosseum was particularly badly affected, with water pouring into the underground tunnels and galleries where gladiators and wild animals once waited before being hoisted into the ancient arena on wooden lifts for staged fights.
At one point the tunnels, which were only recently opened to the public, were submerged to a depth of 15ft, officials said.
The severity of the flooding of the amphitheatre was “unheard of and extraordinary”, said Francesco Giro, a senior heritage official.
He said it evoked the ancient Roman practise of inundating the Colosseum with water in order to stage mock naval battles between gladiators and slaves.
“Following the exceptional weather that hit the capital, the Colosseum, the Roman Forum, the Palatine, the Baths of Caracalla and the excavations at Ostia are closed to the public,” Rome’s archeological department said in a statement.
It was not clear when the sites, which attract millions of visitors a year, would be reopened. Engineers carried out checks to make sure none of the structures had been seriously weakened.
The torrential rain also brought down two large pine trees on the Appian Way, the ancient Roman road, lined with mausoleums and catacombs, which led from the imperial capital to the Adriatic coast.
The Circus Maximus, where Roman chariots once raced, was so extensively flooded that a man was photographed paddling a kayak across it.
UPDATE (a few minutes later): tip o’ the pileus to @scotartt on Twitter for pointing me to Martin Conde’s set of photos of the flooding: Rome, Flooded – Torrential Rainstorm – Roman and the Imperial Forums, Coloseum Valley and the Circus Maximus Underwater. Dott.ssa Astrid D’Eredita` / Fotos: Claudio Valletti / La Repubblica.it