Second Flatiron Trail Boulder is a premier hiking destination in Boulder, Colorado, covering 3.0 miles with 1000ft of elevation gain. Stats: 3.0 miles, 1000ft gain, Moderate. Type: Loop. Surface: Rock/Dirt. Time: 2-3 hours. Fee: Free. Dogs: Yes. Permit: No. Wildlife: mule deer, black bears, golden eagles, falcons, rattlesnakes. Best seasons: Year-round accessible; spring and fall ideal; a true Boulder classic with exposed scrambling. The Second Flatiron trail via Chautauqua Park delivers the quintessential Boulder hiking experience — scrambling up the exposed lower slabs of the massive tilted sandstone formations for panoramic views of the plains and city. Pack plenty of water — desert and high-altitude trails demand more hydration than you expect. Layers are essential above 10,000 feet. Leave No Trace: stay on designated trails, pack out all waste, and respect wildlife and other visitors.