Natural hot springs are geothermal features where heated water flows from the Earth's crust. This heat usually comes from volcanic activity or the decay of radioactive materials deep underground. The water can be rich in minerals, which some people believe have therapeutic properties. These springs can be found in various locations around the world, often in scenic areas like mountains or forests. Popular destinations include Yellowstone National Park in the United States and Hakone in Japan. Many visitors enjoy soaking in the warm waters, which can provide relaxation and relief from muscle tension.