Tourists are once again getting into trouble in Italy, with two American women caught carving their names into Rome’s Colosseum.

The Californians, aged 21 and 25, snuck away from their tour group on Saturday and began scratching their initials into the amphitheatre with a coin. They managed a “J” and an “N” around 8cm high, before taking a selfie with their handiwork.



Police were quick to catch the two Americans and report them for damaging the ancient site. The women may now go in front of a judge and face a penalty.



Defacing the walls is strictly forbidden, as pointed out on signs in both English and Italian. But some visitors think little of breaking the rules as they view the crumbling monument differently from other top sites such as the Vatican, said a spokesman for the Special Superintendency for the Archaeological Heritage of Rome.



“There’s a difference in perception. Museums are treated like churches, sacred places where there are things of great value. Whereas the Colosseum is an incomplete building which has already been robbed,” the spokesman said.



The Colosseum fell into disrepair after its heyday of hosting 73,000 spectators, watching gladiator fights to the death, and was at one point quarried for its stone. While the amphitheatre was completed in AD80, the section defaced on Saturday dates to the 1800s when the pope initiated restoration work.



“It’s not an original wall but it’s nevertheless antique,” the spokesman said.



Antonio Camertoni, impersonating a Roman centurion outside the Colosseum, agreed the tourists were wrong to carve into the stone. “It’s a piece of cultural heritage. They don’t do it at home, but they do it here,” he said, musing that perhaps the site should be closed to tourists altogether.



But the two unruly tourists are an incredibly small minority of around six million people who visit the Colosseum and Roman Forum each year. Johnny Hansen, on holiday from Denmark, said he certainly didn’t intend to leave his mark on the site. “Everyone should have respect for it. They should be fined to make an example. It’s heritage, so you must protect it,” he said.



The sheer number of visitors to the Colosseum, coupled with staffing cuts, makes it increasingly challenging to catch tourists behaving badly. Security was upped at the Colosseum and other sites last month, following threats against Rome by Islamic State, but the focus is on stopping terrorists not rule-breaking tourists.



Police vehicles parked by the amphitheatre and metal detectors at the entrance reflect the new security measures, while inside Colosseum staff continue trying to keep order among the visitors.



“The security is not inadequate from the point of view of terrorism, but the shortage of personnel and the great mass of tourists is a problem, also for other sites,” the Superintendency said.



The Californians’ lawbreaking comes little over three months after a Russian tourist was caught carving a 25cm letter into the Colosseum. The 42-year-old was given a four-month suspended prison sentence and a €20,000 fine, although owing to a lack of funds he has not paid the penalty.



The Russian was the fifth person to be stopped for defacing the ancient monument last year, with others hailing from Australia, Brazil and Canada.