Flagstaff? Super Flag? No, It's Ultra Flag!
Gross Dam Road is unpaved, as is the top of Sugarloaf. I have seen racing bikes on both. 48 miles.

1. Boulder
2. Gross Reservoir
3. Crescent Village
4. Coal Creek Canyon & Peak to Peak Highway
5. Peak to Peak Highway & Sugarloaf
6. Sugarloaf & Boulder Canyon
7. Boulder

You may wish to finish on the Boulder Creek Path and Arapahoe Avenue instead of taking Boulder Canyon all the way into town.