The Flatirons are the iconic range indicative of Boulder, and they are a must-visit for anyone who is in the area for a quick run, some rock climbing, or a day hike. The Flatirons are made up of conglomeratic sandstone of the Fountain Formation, a long formation of the Front Range that stretches from Wyoming down into Colorado. The age of the rock is estimated to be 290 to 296 million years old, while the uplifting of the formation was between 35 and 80 million years ago. Erosion took care of the rest to carve out the slanted spires seen today.
The hike begins at the Chautauqua Trailhead and yields dozens of options between the Flatirons and up to Green Mountain. Follow the signs to First/Second Flatiron; as the trail climbs up a forested crease between the two, you’ll pass a rock climbing area on First Flatiron that will likely be occupied if the weather is nice. Eventually you’ll come to a saddle behind the Flatirons with a great view of Rocky Mountain National Park off in the distance, with Long’s Peak towering over the rest on the right of your field of view.
There are some areas that provide some scrambling for better views, so take care as the slopes can be slippery. Head back the way you came, with many options to extend the hike if you still have time.