Minutes from Downtown Boulder, COHundreds of routes of all grades. Sport, Trad, and Top Rope options available.
Heading west from Boulder, take CO 119/Boulder Canyon Drive into Boulder Canyon. Once you're in the canyon, there are many areas that all have great climbing. For the more traditional climber, there are areas such as Castle Rock (39.9787, -105.4551) and the Happy Hour Crag (40.0033, -105.3939). People looking for great sport climbs should check out the Sport Park area (39.9726, -105.4648) or Lower Dream Canyon (40.0069, -105.4058). For descriptions of certain routes and a list of other areas in the Canyon, I would recommend getting a guidebook from one of the local outdoors stores or the REI in town.
Getting to the majority of the climbing areas requires a Tyrollean traverse, which involves attaching a quickdraw to your harness to a rope (or two) suspended over Boulder Creek and then pulling yourself across the raging water below. It's a pretty awesome experience the first time you do it! Once you are across, the approach can be somewhat steep and there is some loose rock, so be careful hiking up to the crags. When you get to the crags, enjoy the time there, set up a hammock amongst the trees while your friends are climbing, take in the views of the steep canyon walls and the rushing water of Boulder Creek below and just have a blast!