Yellowstone National Park is a treasure that inspires travellers from around the world. New Zealand and Iceland are known for their geysers, but nowhere are there as many as in Yellowstone. At the heart of Yellowstone's past, present, and future lies volcanism. Several times in the last two million years, catastrophic volcanic eruptions occurred here. The latest eruption spewed out over two hundred cubic miles of debris. What is now the park's central portion then collapsed, forming a caldera, or basin covering almost thirty by fifty miles. The magmatic heat powering those eruptions still powers the park's famous geysers, hot springs, fumaroles, and mud pots. The spectacular Grand Canyon of the Yellowstone River provides a glimpse of the interior of the Earth: Its waterfalls highlight the boundaries of lava flows and thermal areas. Rugged mountains flank the volcanic plateau of the park, rewarding both eye and spirit. Yellowstone's wildlife includes the American bison, elk, grizzly and black bears, trumpeter swans, and Yellowstone cutthroat trout. A variety of vegetation types is encountered, from near-desert vegetation around the North Entrance to subalpine meadows and forests on Mt. Washburn. Lodgepole pine covers about sixty percent of the park and constitutes about eighty percent of the forested areas. Yellowstone would be a premier national park for its scenery or its wildlife alone, but its history also resonates with colourful tales of fur trappers - Jim Bridger or Osborne Russell - and explorers and surveyors, with their photographers and artists. William Henry Jackson's photographs and  Thomas Moran's sketches influenced Congress to establish Yellowstone as the first national park of the world, a hundred and thirty years ago. This national park idea has now become a land-use model for many nations, and Yellowstone has evolved from a pleasuring ground and wildlife refuge to be recognized today as an International Biosphere Reserve and World Heritage Site as well.