Sitting atop the active Yellowstone Caldera supervolcano, the park contains fully half of the world's known geothermal features, and standouts including Old Faithful Geyser and Mammoth Hot Springs are popular tourist attractions. Geologically, the park encompasses lakes, canyon's rivers, and mountain ranges. Yellowstone Lake is one of the largest high-altitude lakes in North America. The Lower Falls of the Yellowstone River, at 308 feet, is the tallest of the park's 290 waterfalls.
Biologically, Yellowstone National Park anchors the Greater Yellowstone Ecosystem, the largest intact northern temperate ecosystem on the globe. Sixty species of mammals live in the park, including gray wolves, lynx, grizzly bears, black bears, bison, elk, moose, mule deer, white-tailed deer, mountain goat, pronghorn, bighorn sheep and mountain lions. Wildlife management, especially of the nation's largest public herd of bison, has been controversial.
Eighteen species of fish call Yellowstone home, including the highly prized Yellowstone cutthroat. Many waters inside the park are open to fly-fishing only, and native species are restricted to catch and release fishing. A Yellowstone-specific fishing license is required. Hunting is not permitted in the park.
Recreational opportunities in Yellowstone include cycling, cross-country skiing, hiking on more than 1,100 miles of trails, snowmobiling, lake canoeing and kayaking, and wildlife watching. The park contains nine hotels and lodges with 2,238 hotel rooms and cabins for rent; twelve road-accessible campgrounds offer more than 2,000 campsites; backcountry campsites accessible by foot or horseback require permits.
July is typically the park's busiest month, accounting for almost half of Yellowstone's 2 million annual visitors. During high season, crowds concentrate around Old Faithful and the Grand Canyon of the Yellowstone. For the most relaxed experience, the fall season offers the best combination of weather and elbow room. But even on the most crowded summer day, peace and quiet can usually be found by taking a short walk down any trail. Be advised that Yellowstone Park is one of the last strongholds of the grizzly bear in the lower 48 states, and the usual precautions apply in dealing with bears, bison, and all of the park's wild creatures.