The next time you are in Boulder, Colorado, you might want to check out Eldorado Canyon. "Eldo" is one of the most challenging mountain-climbing experiences in the U.S., featuring plenty of crags, cracks and sheer faces.

Located just outside Boulder, Eldorado Canyon draws thousands of climbing enthusiasts each year from every corner of the world. It isn't that the climb is all that difficult, though routes range from baby beginner to extremely advanced, rather, the complexity of the routes and the confusing nature of the canyon present unique challenges.

In fact, most people require guides if they are going to climb in Eldorado Canyon. It is easy to get lost and wind up on a route that is too difficult for your experience, and you shouldn't try to determine pitch grade without a guide or guidebook.

As far as routes, you'll have your pick once you start your climb at Eldorado Canyon. There are more than 500 ways to scale this beautiful canyon, starting with 5.6 climbs such as Wind Ridge and 5.8 climbs like The Bastille Crack.

If you're really feeling adventurous, try the Iron Monkey, a recently-added 5.14 climb that is sure to get your blood pumping. However, make sure you know your strength and your abilities before you try some of the more treacherous climbs.

This climb is particularly difficult in the height of summer, when humidity adds to the oppressive heat. The rock face becomes slick and therefore difficult to navigate, so make sure you bring a pair of high quality gloves. You'll also need a harness with plenty of gear loops, such as the Black Diamond Alpine Bod harness.

To get to Eldorado Canyon from Boulder, hope on CO Hwy 93 South, then head west on Eldorado Springs Drive, which is just past the city limits of Boulder.

Colorado is one of the best places in the world to go when you need a good climb, and Eldorado is just one option among many. Although you are unlikely to get bored here, check out some of the other areas around Boulder for different challenges.