Of all the waterfalls I have ever been to, Erawan Falls near Kanchanaburi, Thailand, are perhaps the most beautiful. While not the tallest, widest, or most gallons/minute, the clarity of the water and the unique limestone formations make them the most interesting.
The water passes through underground limestone deposits, and comes out loaded with calcium carbonate, leaving layers of limestone over everything and giving the water its unnaturally blue-green color. When I say limestone covers everything, I mean *everything*. Logs in the river are coated with as much as a centimeter of rock, and even leaves.
One really interesting phenomenon is the rocks a the base of the falls... some don't touch the water underneath!!! How? They grow out from the cliff face from the CaCO3 deposits, and you can swim underneath them and have a few centimeters of breathing space.
There are seven steps of the waterfall, spread out over a kilometer and a half, and each of them is different. A couple of the pools are large enough to swim in, and the water is quite nice. Some of the falls have limestone caves filled with stalagmites. Some of the pools have very aggressive fish, which attack your toes. Some of the falls are only ten or so feet tall, and some are around 70 feet.