There is nothing that I love more than exploring the rainforest in South America. I've done it in several different countries, and it is never a letdown for the adventurous.
I've chased caiman, caught piranhas, slept in hammocks and tripped over anacondas. Those were some of the happiest moments in my life.
Most people, though, are probably looking for something a little... milder.
If you want to explore the Amazon rainforest with more comfort (while not missing out on nature), then a river cruise in Ecuador is probably exactly what you're looking for.