The falls occur at a fracture in the Rio Iguazu, which defines part of the border between Argentina and Brazil.
We stayed at the nearby Sheraton hotel (10 minutes walk from the falls) for two days. The other side of the river is Brazil and we also spent one day at the Hotel das Cataras. From either side, you can see across the river to the other hotel.
On the Argentina side, there are two boardwalks: one that traverses the edge of the falls for a kilometre or so and a second boardwalk that crosses the river to take you to a point at the edge of the Devil's Throat.
This aerial photograph (above) taken by Claudio Elias in 2004 gives an excellent view of the falls. Brazil is on the left (you can see Das Cataras) and Argentina is on the right (you can see the old observation tower). The largest single fall is named the "Devil's Throat" and appears just above the midpoint of the photograph.
The Sheraton Hotel (my photo below) is located out of shot, below the bottom edge of the aerial photograph.
