Ecuador's Yasuni National Park, that's where.
I had heard about this rainforest- it is a forest for the entomologist, herpetologist, appreciator of all things small and diverse and complex. Sure, you may see some monkeys, or the footprint of a jaguar in the mud. But the real discoveries are beneath your feet, perched on leaves, or fluttering through the air. Oh, or giving you kisses like this tapir did.
Primary source of information on species richness: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008767