Las Siete Altares (The Seven Altars) is a series of 7 waterfalls. Some of the falls are more spectacular than others, and the further up you get, the more impressive the sight.
Most guides will take you by boat to a small beach from which you can hike through a jungly path to get to some of the waterfalls, but you will probably only get to number 3 or 4.
During our time at the falls, I was able to climb to a couple of the next levels, but it is kind of treacherous -- be careful! One of our guides was a ten-year-old boy who enjoyed jumping off the rocks into the waterfall pools. It looked fun, but I wasn't feeling particularly risky that day.
You can arrange for hikes that will take you from Livingston and go all the way to the seventh altar. These are all day trips, and there are no facilities on the way.