Corcovado National Park is the most remote area of Primary Rain Forest left in Costa Rica. It's claimed to be the most "biological intense place on earth" by National Geographic. The only access is by foot or you can cheat and get a boat to the edge of the park and then walk. A two day walking safari provided enough time to see tapier, all 4 species of monkey, giant anteater, otters, coati, crocs, bull sharks, eyelash vipers, scarlet macaws, tucans and around 100 species of birds. It helps if you have a good guide!