While Rocky Mountain National Park in Colorado is home to some of the classic long alpine rock climbs in the United States, its glaciated valleys also offer a lot of excellent bouldering. Bouldering can be used to warm up for long rock routes, as a cool down in the campground after a full day, or as an end in itself to pursue technical climbing difficulty.
Lumpy Ridge dominates the skyline in Estes Park when you drive into town, but the climbing all lies within the boundaries of Rocky Mountain National Park. While formations such as the Book and the Twin Owls boast many classic multi-pitch lines, there is good bouldering close to the parking lot below Twin Owls. The Jaws boulder just east of Little Twin Owls has some great problems, and numerous boulders can be found below the Book.
Bear Lake Road has several excellent boulders, particularly above the Big Thompson Bridge at the east end of Moraine Park. There is also good bouldering just up the road at Hallowell Park. The south shore of Bear Lake also has several problems hidden in the trees. A short two-mile hike exposes some good bouldering problems on the boulders around Emerald Lake, a stunningly beautiful alpine lake below the steep north face of Hallett Peak.
Many of the classic rock climbing destinations in the park, including Spearhead, Chiefshead, the Diamond and Notchtop, have plentiful boulders at their bases to play on. Chances are, someone has done a problem there, even if it isn't in a guidebook. However, the best bouldering in the park is in Chaos Canyon on the south side of Hallett Peak. Modern test pieces up to V14 in difficulty abound in Chaos Canyon. The heart of bouldering in Chaos Canyon is on the Centaur Boulder and the Automator Boulder.