Iguazù is defenitely a top 3 “to visit” in Argentina. We went for the 2nd time.
It’s only a 1:20 min flight up north, and you can go for 2 days. Although this period (january) is defenitely not the best if you don’t like the heat : compared to that Buenos Aires is ‘cool’. The humidity is 100%.
We first drove to the Brazilian side which is the nicest : it is the only place from where you can see all the falls at the same time. The view there really is splendid. It is quite a fuss to get there though you must wait in line at both the Argentine and the Brazilian costums. Although we drove only about 20 minutes, we were on the road for about an hour and a half. But it is definitely worth it! There is a nice walk, going from the Hotel las Cataratas up to the falls, the closer you get the louder the noise of the falling water becomes. At the end you walk over the water and get really close the the biggest fall. (Take a plastic bag to cover your camera if you want to go to the end)
On the Argentine side there is the biggest fall, called the devils throat, that is really impressive. Last time we were there the Gargantua del Diabolo was hidden by the watercloud, but this time the wind came from the other side and the view was spectacular. The power of the water is so amazing that you can stay there and watch for ages. Then there is the walk over the falls that is grand, you can almost touch the water.
I would say that the Brazilian side is the most beautiful one, but the Argentine is the most spectactular. (So first do the brasilian side, then the Argentine).
But the greatest must be the boat trip under the falls. We did this both on the Brazilian side (a few years ago) and now on the Argentine side, and the last one was so much nicer. With a powerful motorboat you really get close to the falls, and in the end you get soaking wet. (you get a 100% waterproof bag to put your stuff/camera in). From the end of the boat trip up there is another really nice walk up, again close to the falls.
Last time we also did the helicopter tour which was great too. We thought 100 USD for 10 min pp was a but too much to go for a 2nd time…
After 2 days we have seen and felt enough water. In every possible way. Water, water and more water. That’s probably why Iguazu falls are considered one of the biggest falls in he world.