Yesterday my buddy Jef and I went to The Robber's Roost and descended into Blue John Canyon. The canyon was made famous by this guy:
There are a couple of forks that join together to form lower Blue John Canyon, where Aron got stuck. That canyon drops into Horseshoe Canyon, where my dad and I hiked a couple weeks ago. Jef and I did a loop through the slots above Lower Blue John, and it only took us 6 hours. This sign we found at the trailhead info kiosk.
Read the bottom paragraph: the blue pool is NOT in Blue John (like it shows in the preview and movie!).
At a wider section of the slot canyon. We caught the sun perfectly! Some deeper parts of the canyon never see the light of day.