Thousands of Romans were left in the dark - and in the rain
Italy has been hit by a massive power cut - and many parts remain without electricity hours after the unprecedented blackout.
Only the island of Sardinia escaped the power cut, which struck at about 0330 (0130GMT) on Sunday morning.
About 110 trains were reported to have been brought to a standstill across the country - trapping thousands of people.
It is the latest in a series of major blackouts to affect national power grids - north-east United States and Canada were hit last month, and Denmark and southern Sweden on Tuesday.
A power cut left London's underground transport in chaos last month.
The Italian national grid authority blamed the blackout on a malfunction of two major supply lines from France.
French officials confirmed there had been a brief interruption of supply - "probably because of stormy conditions in the zone" - but denied this was the cause of the Italian blackout.
The two countries have a long-standing electricity exchange scheme to help deal with peaks in demand on both sides.
Power has been slowly returning - mainly to northern areas - though officials have warned it will be several hours before the whole country is supplied.
It is an "absolutely exceptional event," said Carlo Andrea Bollino, national grid chairman.
White night in the dark
In Rome, the power cut struck as thousands of people celebrated the city's first "White Night" - an extravaganza of street events.
The failure halted the free underground service provided by the city, and left passengers stranded in underground trains.
Heavy rain had already stopped a number of attractions.
"We're not happy at all. Everything was fine - then it all happened at once and now we're angry and wet," a drenched Roman told Reuters news agency.
The lights also failed inside the Vatican, although emergency generators are now operating there as they are at Rome's hospitals and key government ministries.
Planes are landing and taking off as normal from all Italy's main airports.
Emergency services coped fairly well with the situation, says the BBC's David Willey in Rome, although several accidents have been reported as a result of the failure of traffic signals.
Italy suffered partial power cuts in June, when the system was strained by heavy use of air conditioners and other electric items.
The national grid operator has repeatedly said power demand is growing faster than supply and that imported electricity would not make up for insufficient production in the long term.