The chockstone! It's about the size of a dump truck and has probably been wedged into that spot for thousands of years. In an El Nino year, the avalanche debris fills up this entire chasm, so you can literally walk up to the top of the chockstone.
In a normal year, a few brave souls climb the class ~5.2-5.4 wall just to the right of the waterfall. We weren't comfortable doing that given the remoteness of the location, lack of rope, the weight of stuff we were carrying, and my snowboots were a bit too clunky to try anything crazy. The rocks leading up to the wall were also very slick.