Corcovado is the last preserved virgin rainforest in Central America. Trees over 100 years old and 50m tall.
Wild life is amazing. This area contains 2.5% of world's Flora and Fauna.
The best experience would be by accessing it from Sirene station, which is only reachable by boat. Tour operators charge insane $185.
This is back entrance, Los Planes, which is less known to the public. There is the Rangers station but if you get there on the bike, they will just let you go for free.
Nature is incredible but the wild life is not as rich as at Sirene entrance. Bring a lot of water and food. Hiking boots/long pants would be preferred but I did it in sandals/biking shorts. Not to smart as there are 25 spices of poisons snakes around plus all kinds of other bugs. I didn't see any, which doesn't mean that they were not there.
Enjoy and respect!