Yellowstone National Park

Signed into law in 1872, Yellowstone was the first national park anywhere on Earth. It covers almost 9,000 square kilometers of Wyoming, Montana and Idaho, and beneath it sits one of the largest volcanic systems on the planet. That heat powers more than half of the world’s active geysers, along with steaming hot springs, bubbling mud pots and hissing fumaroles.

Old Faithful erupts roughly every 60 to 110 minutes, and rangers post the next prediction at the visitor center. A short walk away, the Upper Geyser Basin hides dozens more. Grand Prismatic Spring, wider than a football field, glows in rings of blue, green, yellow and orange; see it from the Fairy Falls overlook trail for the full rainbow.

Yellowstone is just as famous for wildlife. Bison graze along the roads, and the Lamar Valley, often called America’s Serengeti, is the best place in the lower 48 states to spot wolves, ideally at dawn with binoculars. Don’t miss the Grand Canyon of the Yellowstone, where the Lower Falls drop 94 meters into a canyon of yellow and pink rock.