Barreirinhas

Barreirinhas needs 2 days: sailing the Preguiças river to the coastal dunes on one, and touring by 4x4 the Lençóis Maranhenses National Park, with its turquoise rainwater lagoons among white dunes, on the other. June-September is the best time, when the lagoons are at their peak after the rains. It's mid-priced, with the 4x4 excursions as the main expense. It's the usual gateway to a landscape that looks like a desert but isn't one: between June and September, thousands of crystal-clear rainwater lagoons form among the dunes, some with fish arriving through underground channels, a phenomenon unique in the world.