Mexico's incredible cave-like sinkholes, once revered as gateways to the underworld by the ancient Mayans, may need their surface openings closed because of pollution from the tourism industry and poor water treatment.
The underground river system is the only source of fresh water for the Yucatan Peninsula but environmentalists fear that if the government does not act, the aquatic wonders may be lost forever.
Al Jazeera's Rachel Levin reports from Tulum, Mexico.
Source: Al Jazeera