The mountain range that rises immediately behind Guaratuba is a national park protecting nearly twenty-five thousand hectares of Atlantic Forest — one of the most threatened ecosystems on earth, of which less than ten percent now survives. The forest here is dense, wet and largely intact, with a high diversity of bromeliads, orchids, palms and primates. The Serra do Lange peak reaches over a thousand metres.
Access is informal and best arranged through a local guide; the marked trail network is limited and signage almost nonexistent. The easiest entry is from the Cabaraquara road, where a small ranger station can suggest a half-day walk. Wildlife — howler monkeys, capuchins, occasionally a brocket deer — is best seen at dawn.