Rocky Mountain
Credit: John Elk III / Getty Images

Marked by small glaciers and snowy meadows, Colorado's Rocky Mountain National Park has hundreds of trails that lead visitors to 72 peaks that reach higher than 12,000 feet. The Continental Divide splits the area into two distinct sections – a dry, icy area to the east and a lush, woodsy area to the west – so hikers can choose their own adventure. 

Don't Miss: Birders flock to this area to spot white-tailed ptarmigans and red crossbills, which make their homes in these mountains. The park is open all year, but summer is the best time to go.