This turnoff near the top of Flagstaff Mountain is accessed via the winding Flagstaff Road. Be prepared for steep inclines and hairpin turns — and watch out for the crazy/brave/super-fit bicyclists going up and down. You'll find interpretive signage and views that encompass all of Boulder and the plains, and you'll be able to see all the way to Denver and beyond. If you come at night, bring a tripod and set a long exposure to catch the twinkling lights below.