ROME — Tourist flows should be monitored at famous sites in Italy in cities like Rome and Florence, with access limited when crowd numbers swell, the culture and tourism minister said on Tuesday.

Italy’s 51 UNESCO World Heritage sites include whole city centers and town squares which have been increasingly worn out by the footfall of visitors over the centuries.

Conscious of the money-spinning power of places like St Mark’s Square in Venice, some officials have floated the idea of charging for access to currently public areas. But Culture and Tourism Minister Dario Franceschini has other ideas.

“You cannot pay entry to a city, or a street, or a town square,” Franceschini said at an event in Rome.

Instead, the problem should be addressed with “new, non-invasive technology that counts people entering … when the number reaches a maximum access is stopped until they flow out.”

In Venice, one of Italy’s most high-profile examples of architectural beauty under strain, campaigners have been demanding for years that the number of visitors be limited.

Last year, heritage protection group Italia Nostra said 30 million tourists were coming to the canal city every year, and proposed a ceiling of 13.8 million annually.

Tourism accounts for 11.8 percent of Italy’s gross domestic product and 12.8 percent of the country’s jobs are in the sector, according to national tourism agency ENIT.

Franceschini said he wanted to attract people to less well-known sites, and encourage tourists “who come and respect the fragility and the importance of this heritage”.

In a further sign of concern over the growing hordes of visitors, Rome announced earlier this month it would fine tourists caught paddling in its myriad baroque fountains.