Río Secreto is a surreal and unique natural reserve near Playa del Carmen, Mexico, that was opened to the public in December of 2007. Visitors to the site are able to hike and swim through the azure waters of a 1969-foot long river that sits inside underground caves. Inside these caves, you will find thousands of impressive stalactites and stalagmites, and once below the Earth's surface, the world goes silent allowing you to truly enjoy the dramatic scenery in peace.

What's really great about Río Secreto, aside from being an exotic destination, is the fact that the 100% Mexican-based organization's mission is based around eco-tourism. In fact, right on their website it says, "All of us involved in Río Secreto passionately support and promote sustainability and social responsibility. Although our company is still very young, we are working to create a culture of environmental awareness and socio-economic responsibility that goes beyond the borders of Río Secreto. Our goal is to share our message and inspire our collaborators, visitors and society at large."

Tours run daily at 9AM, 11AM, 1PM, and 2PM, and last 3 1/2 hours. The price for adults is $69 while tickets for children 4-11 years of age cost $34.50. To book a tour, click here. For a better idea of what to expect, check out the gallery below.

Gallery: Rio Secreto in Mexico

Filed under: Photos, Mexico, Ecotourism, Budget Travel, Central America