Yellowstone National Park, established in 1872, was the first national park in the world, and is known for its wildlife and geothermal features, especially Old Faithful Geyser. The Park spans an area of 3500 square miles, comprising lakes, canyons, rivers, water falls and mountain ranges. The Yellowstone Caldera is the largest volcanic system in North America and has been termed a "supervolcano" because the caldera was formed by exceptionally large explosive eruptions.