Victoria Falls, on the Zimbabwe-Zambia border, is the world's largest sheet of falling water.
From March through May, millions of tulips draw visitors to Keukenhof Gardens near Lisse, Netherlands.
Yellowstone National Park contains the world's largest collection of geysers.
CNN iReporter Jim Denny captured the Perseid meteor shower as it streaked through the sky on Aug. 11, 2013.
Wildebeest cross the Masai Mara River in Kenya. More than a million travel between Tanzania and Kenya each year during the Great Migration in search of food, water and breeding grounds.
At Alaska's Katmai National Park a brown bear grapples with his slippery dinner. The sockeye salmon run starts here in late June and the bears come out for dinner.
The cracking of mammoth chunks of ice in Alaska's Glacier Bay is a sight -- and sound -- to behold.
Some 340,000 trees line Jinhae's streets, rivers and train tracks, and dot surrounding mountainsides.
Glimpses of this spectacular light show are visible in the Northern Hemisphere's auroral zone near the northern magnetic pole. These swirling lights -- mostly green, but red and blue lights glow at higher altitudes -- are produced when charged particles in the magnetosphere and solar wind collide with atoms.