Iguazu borders between Brazil and Argentina
To visit both sides of the falls, one must cross the borders between Argentina and Brazil
If one is at hotels in Argentina and want to visit the iguassu falls in Brazil and vice-versa one must bring the passport and the covid-19 vaccine proof (two doses). Children under 12 years old dont need it.
People bringing a passport no need to fill in forms anymore to cross the borders, must stop to get it stamped at the borders.
Borders between Brazil and Paraguay
To enter Paraguay and travel further one needs to stamp the passport at the border and show the yellow fever card (no need any more to fill in the healthy declaration)
No need any requirement for children under 12 years old
For people that visit ONLY Ciudad del Este city, they don't require anything. People usually go to Paraguay for shopping because of the duty-free market.
There is a small waterfall called Monday falls near Puerto Franco town. One can also visit the Itaipu Dam from the Paraguayan side. In the city, there is the street market and also a souvenir shop.
Note: National Park in Iguassu Brazil is open also on Mondays
For people traveling in Argentina, it is better to cash dollars on the blue dollar rate. Bring the new blue dollar bills. They give a poor rate for 50, 20, 10 and 5 bills. The bills must be in excellent condition. It is better to get money in Buenos Aires, rates are better there and the WU bureaus in Puerto Iguazu always run out of money.
Since November 5th, some foreign credit cards have been using the blue dollar rate in Argentina.