The Front Range is genuinely close. From downtown you can be at Red Rocks in 25 minutes, on Lookout Mountain at Buffalo Bill's grave in 35, hiking the Flatirons in Boulder in 45, or soaking in the hot springs at Idaho Springs in an hour.
Golden, only twenty minutes west, packs the Coors brewery, the School of Mines, and a block of intact 1880s main street into the gap where Clear Creek leaves the mountains — an easy half-day with Dinosaur Ridge and Red Rocks just to the south.
Climb a little higher and the trips get grander. Loveland Pass puts you on top of the Continental Divide at nearly 12,000 feet in just over an hour and a quarter, with tundra walks within steps of the car. Rocky Mountain National Park is a comfortable day at 90 minutes each way through Estes Park, and Colorado Springs with the Garden of the Gods is about the same to the south. In summer (June to early September only) the drive up Mount Blue Sky is North America's highest paved road and one of the great altitude experiences without putting on a backpack.
