The beaches close to Niterói [1]’s center are polluted, but if you take a bus due south—from the ferry terminal, take any bus marked “Itacoatiara”—you will encounter some surprisingly unspoiled and very attractive beaches, among them Piratininga, Camboinhas, Itaipu, and the most spectacular of them all, Itacoatiara (about 45 minutes from Niterói’s center), which is framed by lushly forested hills.
From here, you have unrivaled views of Pão de Açúcar [2] and Corcovado [3] across the bay. All of these beaches are well equipped with barracas where you can feast on fresh fish and seafood.
Links:
[1] http://www.moon.com/destinations/brazil/rio-de-janeiro/near-rio-de-janeiro-city/niteroi
[2] http://www.moon.com/destinations/brazil/rio-de-janeiro/rio-de-janeiro-city/sights/urca/pao-de-acucar
[3] http://www.moon.com/destinations/brazil/rio-de-janeiro/rio-de-janeiro-city/sights/cosme-velho/corcovado