For those who want to get muddy, jump over fire, or just wear themselves out on the road and in the water, there have never been more race options than there are these days. There's the Tough Mudder, the Warrior Dash, a triathlon in every city, and even zombie-themed runs. The Mile High City's Merrell Oyster, however, offers something a little different: an urban race that is challenging to the mind and body. Denver's Oyster (this year, it takes place on August 25, 2012) takes teams of three on a three- to six-hour scavenger hunt race by bike, foot, and water slide all over downtown, as they, like contestants on 'Survivor,' try to solve seven riddles.

When we took on the race last year, we crossed the finish line in 3.5 hours, having biked to a paintball coliseum and nailed the bull's-eye, hoofed it up and down 20 flights of stairs, skidded down a giant Slip 'n Slide, schlepped 40-gallon water jugs across a parking lot, and biked to a graveyard to photograph a statue. The best mission was the last: At Deschutes Brewery, we were presented with six glasses of beer and asked to identify the style of each. We took our time, even though it cost us the first-place finish, because really, it's about the journey, not so much the destination. [$85; oysterracingseries.com]