If city life has you feeling overwhelmed but with no time for a real getaway, head to the Rocky Mountain Arsenal National Wildlife Refuge. Once the site of a chemical weapons manufacturing center, the former federal facility is now an expansive nature reserve in the heart of metro Denver that's open from sunrise to sunset. There are twenty miles of easy hiking trails, as well as trails for biking; along the way you'll see bison, deer, prairie dogs and incredible birds of prey. For those who'd rather enjoy the great outdoors without getting out of the car, the refuge also has an eleven-mile wildlife drive.