Maranhão's premier attraction, this 1550-sq-km national park encompasses expanses of white sand dunes that run along the coastline for more than 70km and up to 50km inland. The park is also home to beaches, mangroves, lagoons and interesting fauna including turtles and migratory birds.
Its landscapes are particularly impressive from May to September, when rain filtered through the sand forms crystal-clear pools and lakes between the dunes; these are fantastic for swimming.