The ancient citadel of Machu Picchu is one of the world’s most famous tourist destinations. More than 30 years ago, UNESCO added the historic site to its World Heritage collection, calling the Incan sanctuary in Peru “among the greatest artistic, architectural, and land use achievements anywhere.” But the inundation of tourist crowds to Machu Picchu has taken a heavy toll on the site and its conservation, and soon, tourist access to this popular destination will become significantly limited.

Peruvian authorities have announced new measures to lessen the impact of tourism to Machu Picchu (reportedly due to pressure from UNESCO, which, according to the Guardian, has threatened to add Machu Picchu to its list of world heritage sites in danger).

Beginning July 1, all foreign visitors to Machu Picchu must hire an official guide to enter the ancient site and, once there, will be required to follow one of three pre-designated routes through the citadel complex, according to a statement from the Latin American Travel Association. Previously, guides were recommended, but not obligatory, and tourists were allowed to roam the Incan citadel more or less independently, following any marked route they pleased.

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The new measures, introduced by Cuzco’s Ministry of Culture, will further maintain that tickets to Machu Picchu grant entry for a specific time period—either morning (6 a.m. to 12 p.m.) or afternoon (12 p.m. to 5:30 p.m.). Travelers wanting to tour the grounds for longer than their allotted time period will need to buy tickets for both time slots. Ticket pricing, as of now, remains the same.

Overcrowding has become a growing issue at many popular tourist destinations around the world. While tourist entry numbers at Machu Picchu have been controlled before, this recent measure is a major gesture toward keeping visitor levels to the site sustainable in an effort to preserve one of Peru’s most mystical ancient attractions.

“Machu Picchu is one of Peru’s most important tourist sites,” Tony Mason, CEO of the Latin American Travel Association, said in a statement. “We anticipate that the new system introduced by [Cuzco’s] Ministry of Culture will regulate the flow of travelers entering the site and help preserve the authenticity of this national treasure.”

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