Sand dunes transform into magnificent turquoise lagoons during the rainy season. Two rivers that run through the Lençóis Maranhenses push sand from the interior of the continent to the Atlantic Ocean, depositing thousands of tons of sediment. In the park, though, the sand doesn’t stay put, according to Smithsonian Magazine. During the dry season, strong winds whip the sand back inland. Water from the torrential rainstorms in the valleys between the dunes creates thousands of crystal clear lagoons.