Lencois Maranhenses

Declared in 1981, it protects a landscape unique in the world: an extensive field of white sand dunes that looks for all the world like a desert, but which through the wet season (between January and June) fills with thousands of lagoons of crystalline rainwater trapped between the dunes, forming natural turquoise pools that dry up almost completely through the driest months of the year. Its name — the bedsheets of Maranhão — describes exactly that look of rippling white sheets spread over the landscape. Despite its desert appearance, it receives more than 1,600 mm of rain a year, far more than most deserts in the world, which makes its geological formation an unusual case of dunes in a humid climate.