The same geothermal heat that can help you reduce your electricity bill is responsible for some of the world's most stunning natural wonders: Hot springs.
When hot water bubbles up through the Earth's crust, the resulting pools are soothing, mineral-rich springs that have been used for medical, therapeutic, and spa treatments for centuries -- and also leave behind minerals and sediment that create dazzling landscapes.
Grand Prismatic Spring and Midway Geyser BasinYellowstone's Grand Prismatic Spring, at 370 feet across, is the third-largest hot spring in the world, and the biggest in the United States (the other two are in New Zealand); the temperature ranges between 147 and 188 degrees Farenheit.
The location of the spring -- atop a mound of earth -- means it's surrounded by stepped terraces, and the spring gets its color from a variety of factors: The blue water changes pales as the depth changes, the green outer ring is algae, and the yellow, red, and orange are the borders of the spring.
Photo: Wikimedia Commons