The Iguazu Falls, at the northern extreme of a narrow outcropping of Argentina, is the second largest waterfall in the world, and it's got to be the most beautiful. The further north you get, the more green and lush the vegetation is, spotted with red, yellow, white. Some of the roads on the way were just the rusty red-brown dirt and stones that are everywhere here.
I've never been in a jungle, but the national park near the falls *sounds* just like I always imagined one would: it's absolutely full of noise-- buzzing, tweeting, rustling, woops and maybe some growls-- from every direction. Most of the time you can't see where it's coming from, but in my four hours I saw tribes of big-cat-sized coaties (the Ferengi of the park, walking unafraid amongst people, pulling coke cups out of the trashcans), a nest of fantastic green birds and one tall white graza (and lots of other birds), monkeys who were suddenly harvesting all around me at one point (if I were 10 meters in the air), and insects (including lots of different butterflies) galore.
The river splits into dozens of smaller falls (and one huge one), with copious greenery throughout. I've never seen an area so full of life. There aren't very many "trails", and all of them very over-engineered, but they're good and bring you close enough to the falls to feel the spray. Half a day was not nearly enough, but it was what I had to give.
Note, the pictures below don't show very well the biggest waterfall (which I did't get close to, because of the trails I chose), but just imagine all of the other waterfalls combined.