there is a secret "hidden" trail that diverts from School House Gap Trail and takes you to a White Oak Sinks. WOS is no longer maintained by the Great Smoky Mountain park service since the sinks themselves are now considered too dangerous for the random park visitor.

The White Oak Sinks waterfall drops into a bat cave that has now been gated over with a metal gate to keep astray park vistors from falling in or entering the cave to explore.

I have a gallery of images from this hike, here. http://www.pbase.com/lundy/school_house_gap__secret