Death Valley National Park's desert environment includes canyons, mountains and salt flats. — Gary Yeowell/Getty Images

4. The largest organism: Pando Aspen Colony, Utah
Colonies of aspen trees share one root system, and Pando, known as the Trembling Giant, covers more than 100 acres in southern Utah's Fishlake National Forest and weighs an estimated 6,600 tons. Although there's some debate on the matter, most experts hold that Pando is the country's largest organism by weight. Regardless, it is one of the country's most spectacular specimens, especially when its leaves turn color in fall.

5. Hottest and lowest: Death Valley National Park, Calif.
Death Valley is as extreme as it gets. Not only is it the largest national park in the Lower 48 with over 3 million acres, it's home to the lowest spot in the Western Hemisphere: 282 feet below sea level at Badwater Basin. The park also scored what has now been confirmed to be the planet's all-time hottest high temperature, 134 degrees Fahrenheit on July 10, 1913. (A town in Libya claimed 137 degrees in 1922, but that measurement was debunked in 2012.)

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