Yellowstone National Park

The incomparable Yellowstone National Park occupies 3,470 square miles of the Rocky Mountains in northwest Wyoming, was the World's first national park when created in 1872, and is both the second largest in the USA outside Alaska and the fifth most visited - and would be even more popular were it not for its rather remote location and limited visitor season; because of the northerly location and high elevation (mostly over 7,500 feet) the park is fully open for only seven months a year though is still partially accessible at other times for snow-based activities.

The appeal of Yellowstone is based on a unique combination of three elements, any of which in isolation would still make the area famous. First, and most remarkable, are the approximately ten thousand active geothermal features - geysers, hot springs, fumaroles (steam vents) and mudpots, which are found over one third of the park, in a circular area that was several thousand years ago part of the caldera of a huge volcano, and is thought to be close, in geological timescales, to another large eruption.

The majority of these energetic areas are located close to the main roads so are easy to visit though there are plenty more lesser-known regions in the backcountry. One half of all such features on Earth are found within the park, as are nearly 50% of all geysers - Yellowstone National Park has around 450 of these, out of a worldwide total of 970. The main thermal areas are at Heart Lake, Mammoth, Norris, Shoshone, West Thumb and the Upper, Midway and Lower Geyser Basins - this latter is home to Yellowstone's most famous geyser, Old Faithful.

Secondly, the park has beautiful mountain scenery, with high peaks, forceful rivers flowing through steep-sided ravines and over frequent waterfalls and cascades, the 130 square mile Yellowstone Lake plus many smaller lakes, and the Grand Canyon of the Yellowstone River. This is the largest canyon in the park, 20 miles long and up to 1,000 feet deep, but made more exceptional by the striking colors and forms of the jagged, eroded volcanic rocks that comprise some of the canyon walls.

The third component is the wildlife. Yellowstone National Park is the last place in the USA where bison still roam in their natural state, and has the greatest concentration of grizzly bears south of Canada. The park has several hundred wolves, flourishing since their reintroduction in 1995, and many more black bears, together with elk, moose, deer, bighorn sheep, and numerous smaller species. The two best locations for wildlife viewing are the Hayden and Lamar valleys, both towards the northeast of the park.