Deep beneath the Earth's surface, temperatures soar high enough to boil water, spin turbines, and power entire cities. Geothermal energy, which is heat drawn from the ground itself, is one of the cleanest and most reliable power sources available.
Unlike solar panels and wind turbines, geothermal plants produce electricity around the clock, regardless of weather or season. A handful of countries sit atop the right combination of volcanic activity, underground water, and fractured rock, making commercial geothermal power possible.
In this gallery, we look at the 15 countries with the highest geothermal power-producing capacity, which is a measure of the total amount of electricity produced by the nation's power plants at any given moment. Click to reveal them.