If you just want to enjoy the scenery at your own pace with lots of stops or none at all, hit the Peak-to-Peak Byway between Estes Park and Blackhawk. The 55-mile designated scenic byway lies along the eastern flank of the Continental Divide and includes glimpses of several peaks: Mount Meeker (13,911 feet), Longs Peak 14,256 feet), Ouzel Peak (12,716 feet), and Pawnee Peak (12,943 feet). You get the idea: You’re driving from peak to peak, or at least in their long shadows.
The most popular time of year to do this drive is in the fall, in mid- to late September when the leaves of the many aspen trees are turning bright gold, orange, and red. It’s a picturesque drive or ride on a bike as the road’s wide shoulders have room for both cars and bicycles.
From Denver [1] take Highway 6 to Highway 119, which merges with Highway 72 (and becomes Highway 72) until it becomes Highway 7 before entering Estes Park. You will drive through Blackhawk, Nederland, and Allenspark before reaching Rocky Mountain National Park [2]. The drive takes at least two hours, but you can always return on a different, more direct route.
Links:
[1] http://www.moon.com/destinations/denver
[2] http://www.moon.com/destinations/denver/excursions-denver/rocky-mountain-national-park