Cycling beautiful Flagstaff Road
4.6 miles from 5,731’ to 7,705’ gaining 1,975’ at 8.1% average grade.
From the Colorado Daily “5 Classic Boulder Road Rides” 8-25-14 article:
“Breathtaking views of the Flatirons mark this iconic Boulder climb, where the pros battled it out for a stage win in the 2013 USA Pro Cycling Challenge. Through November, Flagstaff Road is closed to cars and cyclists from 8:30 a.m. to 3:30 p.m. Mondays through Fridays, so save this ride for evenings and weekends.
Route: From the intersection of Broadway and Baseline Road, head west on Baseline towards the foothills. The 1.3-mile false flat up Baseline is a grind, but the real climb starts at the intersection with Gregory Canyon Road. You'll get a break at the traffic light controlling a short section of road that's one-way. Then, keep an eye out for the Flagstaff House — the climb gets easier after that. Pedal, pedal, pedal until you reach the amphitheater road. Now you get some dessert after eating all your vegetables — tuck in for one of the best descents in Boulder.
For the hardcore, the "Super Flag" version of this ride goes past the amphitheater up to the set of mailboxes at the top, at around 8,000 feet. It's "only" another two miles, but the majority of it averages a more-than 10 percent gradient.”