We crossed from Brazil into Argentina on our second day in Iguacu (Iguazu in Argentina) to see the falls from the other side of the river. From what we had heard and read, the Argentina side of the falls was far more extensive and would take five or six hours to explore. After our short/long journey crossing the border (short geographically, long due to bus transfers, immigration, currency exchange, etc.), we didn't have time to see it all before the park closed but we had a very different experience from our prior day at the falls. While the Brazil side is new and modern and relatively "user-friendly", the Argentina side is much more rustic. You walk through the entrance and are almost immediately in the jungle. You know this by the signs warning of dangerous animals that could kill you (see pictures below). The signs aren't accompanied by any tips on what to do if you come across these deadly creatures, just that you have a good chance of meeting them and good luck on your journey. I guess the snakes and rabid monkeys were out of town or sleeping because we were lucky to avoid them. Once we got to the falls, we took a long slippery stone path down to the river and boarded a boat that would take us under the falls. It was quite an experience and despite our panchos, we got soaked. After the boat ride, we hiked back to the exit and returned to spend our final night in Brazil.
Tip: When visiting the falls, be sure to wear pants or use bug spray. We got tons of mosquito bites and have been itching for days. We were also attacked by these tiny biting flies that make you bleed. They don't really hurt but you look down and all of a sudden you're bleeding. The joys of the jungle.
P.S. - The creatures below will steal your food...right out of your hand. We don't know what they are but they look like a cross between raccoons, opossums, and ant eaters. As soon as Sara opened a package of crackers, about six came out of the woods and one jumped on the table to try to steal a snack. We witnessed one steal someone's sugar packet right off their table. Aggressive little things.