The Osa Peninsula can be reached by air or by land. 371 kms from San José following the Interamercan Highway until Puerto Jiménez. From this point there are roads to the coast as far as the station at Sirena, 60 kms. away.
Corcovado National Park is one of the protected wilderness areas with the greatest biodiversity in Costa Rica. It ranges over the western sector of the Osa Peninsula on the southern Pacific coast and protects 41,788 hectares of shallow lagoons, marshes mangrove swamps, rivers, rainforests, low altitude cloud forests and 46 kms. of sandy coasts.
These habitats provide refuge for endangered animals, such as the tapir and crocodile (both frequently seen at Corcovado Lagoon), ocelot cougar, giant anteater, harpy eagle (the largest bird of prey in the world), and the scarlet macaw (which has the largest population in the country). Other protected species are howler spider squirrel and white faced capuchin monkeys, great tinamou, silky anteater, poison dart frog, glass frog (with transparent skin) cayman, bushmaster snake, and leatherback, olive ridley and green turtles that nest at Llorona Beach.
The forests are tall thick and dark, dotted with holillo, and other palms where there is little or no drainage. Some of the most important species are purple heart, nargusta, espave, crabwood, and silk cotton.
Identification has been made of 500 species of trees, 140 mammals, 367 of birds, 40 of freshwater fish, 117 of amphibians and reptiles (including 32 species of snakes and 48 of frogs and toads), and it is estimated that there are some 6,000 species of insects. Furthermore, there are deposits of alluvial gold, a metal that attracts invaders who destroy or alter the natural invironment.
The climate at Corcovado on the coast and plains and in the valleys is generally hot and very humid. The climate in the highlands, which reach 745 meters above sea level, is mainly cool, more as a result of clouds than the height.