I think he is referring to the "Lawson Hole" which is right above Mile Hi rafting headquaters off of I-70. Directions from WP:
"From Winter Park
Take HWY 40 South over Berthoud Pass to I-70 EAST. The first exit, only 1 mile, will be exit 233 (Lawson). After the stop sign about 100 yards you will see Alvarado Road on the right. Cross over the river, Alvarado bends to the right and you will be at Mile Hi Rafting."
Head to the next entrance above the rafting house and you will be at the hole.
Get it while it is above 300, I was there last weekend when it was over 400 and had a good time.