America’s oldest and easily its most famous national park, YELLOWSTONE NATIONAL PARK attracts three million visitors every year (97 percent of them in summer), for good reason; the sheer diversity of what’s on offer is mind-bending. Not only does Yellowstone deliver jaw-dropping mountain scenery, from the scintillating colours of the Grand Canyon of the Yellowstone to the deep-azure Yellowstone Lake and wild-flower-filled meadows, but it’s jam-packed with so much wildlife you might think you’ve arrived at a safari park. Shambling grizzly bears, vast herds of heavy-bearded bison (buffalo) and horned elk mingle with marmots, prairie dogs, eagles, coyotes and more than a dozen elusive wolf packs on the prowl. What really sets Yellowstone apart, however, is that this is one of the world’s largest volcanoes, with thermal activity providing half the world’s geysers, thousands of fumaroles jetting plumes of steam, mud pots gurgling with acid-dissolved muds and clays, and of course, hot springs. The park might not look like a volcano, but that’s because the caldera is so big – 34 by 45 miles – and because, thankfully, it hasn’t exploded for 640,000 years.