03/18/2010 05:12 am ET | Updated May 25, 2011

Colorado's Endurance Races: Which Ultra-Race Is The Gnarliest? (VIDEO, VOTE)

We noticed that Lance Armstrong has been touring Colorado promoting his latest project, a documentary about the Leadville 100 mountain bike race that he's participated in the last few years. While the Leadville 100 is unquestionably an intense affair, we figured there has to be some similarly gnarly endurance races in Colorado that haven't gotten as much attention, so we did a little research and put together a slide show featuring the craziest events.

Vote for the most intense event on the slide show below:

Colorado's Gnarliest Competitions