Whilst technically these falls are not on the Blue Mountains, I thought them worth a mention as they are some pretty spectacular falls and easy to get to. Located just 6 minutes from the Kanangra Walls lookout, at the base of a zillion steps and stairs you will arrive at a nice viewing platform with a great view of the falls and the plunge pool at their base. I suspect that pool is popular in summer to cool off, but, by the time you top those steps and stairs going back up, I doubt you will still be cool.
Before you descend, it says 1 hour - Hard. 6 minutes to the falls, about double that to come back up with a couple of breaks on the way, but an hour, hmmmm.
There appears to be other falls and cascade down below these but I did not scramble down for a look. A really nice looking set of falls these ones, worth the effort if you are out this way.