This hike is a little tricky to find for it is not well marked on the road. I was lucky and went into Boulder and put it into my Google maps, and even then it said you have arrived and I looked around to see no signs or anything, just a little side road that was easy to miss. You have to take that side road for a little ways and then you see signs for the Upper Calf Creek Falls. I do know it is about 10 miles outside Boulder close by the Hells Backbone road. The hike heads down a steep huge Boulder where the trail is only marked by Carins. The trail varies from being a very distinctive path, to having to pay very close attention to the Carins to stay on the path. Pay super close attention to the Carins for it is so easy to get off the path and in scary situations, and if you loose Carins turn around quickly until you find those Carins. The waterfall here is beautiful. I read that the Upper Calf Creek is preferable over the Lower for there is. It the issue of so much Poison Ivy, and less crowds with just as pretty of a waterfall. The hike is only about a mile in and a mile back, unless you loose those Carins and then it can add quite a bit of distance on your hike. Stay close together as a group. I thought I was good at keeping my eye out for those Carins but many get lost easily so be careful. I got myself in a scary situation after loosing the trail, and would highly advise others to be cautious and vigilant about making sure they don't loose site of those Carins.