Blue Hole Falls can be found on the Grundy Forest Loop trail, about one-half mile from the Fiery Gizzard North Trailhead.  "Blue Hole", as it is known locally, is a pristine mountain creek waterfall in an idyllic setting, with a good swimming hole at its base.  

From the trailhead, turn left at the loop trail's "split", following the trail downhill, past the site of a former Native American campsite at the "rock house"; and then past several 400 year-old hemlock trees -- some of the oldest in the park.  Blue Hole will be on your left, just after you descend a steep wooden staircase just beyond the falls. Be careful -- rocks are slippery -- and no jumping is allowed, due to the many submerged rocks in the pool area.  

You can return to the trailhead the way you came, or continue on the Grundy Forest Loop trail to see Hanes Hole Falls (no swimming there) and a 1/3-mile side-trail that loops you through the 1930s-era Civilian Conservation Corps campsite.  When you complete the "CCC Loop," turn left onto the Grundy Forest Loop trail to return to the trailhead.

Along the way, portions of the Grundy Forest Loop trail runs along both Little Fiery Gizzard and then Big Fiery Gizzard Creeks.  At one point, you'll come to the place where the two creeks combine to form "Fiery Gizzard Creek" (no adjective in front of "Fiery" anymore!).  Along this section of trail, please take care to stay on the trail at all times and get your head out of your phone, as a mis-step or trip could send you over the edge and down into the rocky creek.