The most interesting and intense stuff that I'm aware of around here are the boulder caves in the Lost Creek area. Way too interesting and intense for me. Imagine piles of huge buried boulders hundreds of yards long with an ice-cold stream running through and under. At least one caver has died in there. There are also some short sections of sculpted granite narrows up in the mountains near Deckers and Aspen that come to mind. I'm pretty sure I ran across one of those up in Lost Creek, too, but that was 35 years ago and I might be putting it in the wrong place. They aren't very long or deep, but they're darned dangerous.