The pair, aged 24 and 25, had climbed up to the second ring of the ancient gladiator arena at dawn on Monday, but were spotted by an early riser who alerted the police.
They admitted to having broken in “to drink a beer” in the early hours, and were given an 800 euro ($905) fine, a police spokesman told AFP, without providing any more details.
It was not clear how they had got into the 2,000-year-old structure, which closes to visitors at 4.30pm.
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This was the latest in a long series of reports of tourists behaving badly at famous tourist sites in Rome.
Such incidents were more frequent before the pandemic, when the Colosseum was visited by around 25,000 people daily.
In 2017, two Brazilian tourists injured themselves while attempting to break into the Colosseum at night.
In the past, judges have come down hard on Colosseum vandals, with one Russian tourist fined €20,000 for carving a giant ‘K’ into one of the building’s pillars.
A bill approved in 2016 introduced the specific offence of defacing or damaging cultural heritage or landscapes, and increased the penalty to a maximum of five years’ imprisonment.
While graffiti is the biggest problem at the Colosseum, there have also been numerous cases of visitors attempting to steal bricks and other fragments of the building as souvenirs.