At the end of the road from El Soberbio you cross the Río Yabotí and arrive in the Parque Provincial Moconá. There's a visitors center, walking trails and a restaurant. Boat trips (AR$250) are essential if you want to get a good look at the falls as they flow from the Argentine side of the river toward Brazil; from land here you are just able to see the top where the water drops off. January to March is normally the best time to visit.
The park website tells you the visible height of the falls; it's crucial to check before coming. When water levels are high the Yabotí may be impassable.
For good views of the upper Río Uruguay hike the 1.8km El Chachi trail. The shorter but more challenging La Gruta trail leads to a small cave with a narrow waterfall.