Barreirinhas is a beautiful village in Maranhão, which has one of the greatest treasures nationwide (and internationally speaking, I would add): the Lençóis Maranhenses. Extensions and extensions of dunes that house natural pools of blue waters between the mounds of sand. A show that, if you get to see it in good time, this is in the rainy season (best is between March and October), you will enjoy and remember forever.
Another excursion that you can do around Barreirinhas is to Atins (waterway) and Tutóia (road). They are picturesque fishing villages that are also the gateway to two deltas: the Preguica River and the Parnaíba River, respectively. Atins, in particular, is a visit highly recommended for its isolated location, and because along the way you will see varied things: remote and deserted beaches, some cool lighthouse, an island full of cappuccinos... (introduced species)