Natural Bridges International Dark Sky Park, Utah, USA
Credit: Jacob W. Frank / Getty Images

Visitors can bask in an awe-inspiring view of the night sky transected by one of the three natural, rocky "land bridges" formed in canyons here by rushing water thousands of years ago. The 12 square-mile site is "exemplary of the darkness of the Colorado Plateau" and "one of the darkest locations in our system," says Barentine.