Poza Azul

Poza Azul is the best-known of the hundreds of spring-fed pools scattered across the Cuatrociénegas valley, and the main gateway to the protected area. It lies about 9 kilometers southwest of town, a circle of startlingly clear turquoise water a little over 5 meters deep, set among desert scrub and grasses.

The valley is a federal flora and fauna protection area of more than 84,000 hectares, and a Ramsar wetland of international importance. Its isolated pools are home to more than 70 species found nowhere else, including fish, snails, and the Cuatrociénegas box turtle, as well as stromatolites: living mats of microbes like the ones that helped fill Earth's early atmosphere with oxygen. Scientists come here to study what life may have looked like billions of years ago.

To protect that fragile life, swimming in Poza Azul is no longer allowed. Instead, you walk raised trails and viewpoints around the water, including the El Borbollón path to a spring that bubbles up from the ground. The visitor center has displays in Spanish and English on the valley's plants and animals, and it is where you hire licensed guides for sites like the gypsum dunes.