Rocky Mountain National Park
Trail Ridge Road, the highest through road in the USA (12,183 feet), with elk by the roadside.
Tip: From late May to October you need a timed-entry reservation.
One of the 11 national parks where visitors from abroad pay $100 a person on top of the entrance fee, since 1 January 2026. With two or more of them on your trip, the $250 annual pass is cheaper: travel info.