Parque Estadual de Ilhabela was established in 1977 and encompasses virtually the entire interior and eastern face of the island, plus several offshore islets. The park protects a remarkable sample of Atlantic Forest — one of the world's most biodiverse and most endangered biomes — along with 365 catalogued waterfalls, pristine beaches reachable only by trail or boat, and peaks rising above 1,300 metres. Wildlife includes the woolly spider monkey, the maned sloth, and dozens of bird species found nowhere else.
The park's trail network is the main reason most visitors come to Ilhabela. Trails range from the 30-minute walk to Cachoeira Pancada d'Água near the north of the island to the full-day odyssey to Praia do Bonete in the south. To enter the park on foot or by bicycle, register at one of the park entrances; guided tours are available and recommended for longer routes. Rangers can provide up-to-date trail conditions, which change significantly between the dry season and the wet months when rivers run high and paths turn slippery.