During your trip to Argentina, if you are leaving from Buenos Aires, you need to be ready for a long journey to get to Iguazú. However, there's no doubt that it will be worth to discover it. If you take the bus from the capital it will take you at least 18 hours. If you are leaving from Salta it is even longer as you will spend at least 26 hours on the road.
If you want to travel more comfortably, or if you really don't have much time to spare, then travel by plane. This will gain you some precious time because if you travel from the capital it is 18 hours by bus. However, the flight is a bit less than 2 hours by plane. The three frontiers
So you finally made it to Puerto Iguazú? Before you go off to visit the enormous waterfalls which are a UNESCO World Heritage site, you should first go for a walk around town. Just the name "Tres Fronteras Avenue" should give you a clue about what to expect. Facing the Iguazú and Paraná rivers, you are between three towns in three different countries. There is a landmark on each of the banks. Puerto Iguazú is in Argentina, Foz do Iguaçu is in Brazil, and Ciudad del Este in Paraguay. It's a unique place where you can see three different countries with just a glance.