One of the most picturesque beaches near Rio, Prainha is backed by cliffs and thick forest. The sea can be rough, but it's a favorite among surfers. It feels secluded during the week, but gets crowded on weekends (go early to beat the crowds).
You'll need to take a taxi or a ride share to get to this beach, which is roughly 22km west of the Jardim Oceânico metro station in Barra da Tijuca.