Green Mountain via Chautauqua Park

Starting from the popular Chautauqua Park trailhead, head west on the main trail to the first branch off onto a smaller trail that will take you toward Baseline Road. Follow this trail until it eventually connects with Gregory Canyon Trailhead—you can park at this trailhead if you wish, but miss out on view of the Flatirons.

Head out on the main Gregory Canyon trail that heads due west into the mountains. This trail will begin to climb pretty rapidly up through the canyon, so be ready. About a mile of climbing later, you will reach the high point of the canyon and have a mostly flat section for about half a mile. At the end of this flat section will be a ranger station; continue straight ahead on Ranger Trail.

On Ranger Trail, continue the climb west until you reach a trail junction. Either direction will get you to Green Mountain Summit, but taking a right will have you on the shorter, steeper route and a left turn will take you on a route that's not as steep, but considerably longer. Choose your direction based entirely on preference; if there's snow on the trail, however, it's better to take the left route.

Either way, the climb will continue for a mile and a half on the right route or about two and a half to three miles on the left route. As long as you don't leave the trail, it will be very straightforward—in an hour or two you'll find yourself on top Green Mountain with views of the Front Range, Boulder, and the plains to the east.