Rome's 2,000-year-old Pantheon started charging for entrance Monday, with tourists paying five euros ($5) to see Italy's most visited cultural site.
The building, one of the city's oldest and best loved, is currently a consecrated church and part of the proceeds from ticket sales will go towards the diocese of Rome, while the rest will go to the culture ministry.
Minors and Rome residents are exempt from paying.
The new charge "won't stop many people coming to visit", French visitor Camille Piallat predicted, as he queued to buy his ticket in the sunshine.
Engineer Tim Witte, visiting from America, told AFP he thought five euros was a "very reasonable" price.
The other major churches in Rome, including St Peter's Basilica, are free to visit, but museums and monuments such as the Colosseum are ticketed.
One of the best-preserved relics of ancient Rome, the Pantheon is famed for its extraordinary dome, which measures 43 metres (140 feet) in diameter and includes a circular opening through which light and occasionally rain fall.
It was built as a temple in the first century BC before being radically rebuilt under Emperor Hadrian at the start of the second century AD.
After falling into neglect, it was given a new life after being consecrated as a church in the seventh century under Pope Boniface IV.