Hot springs happen because Taiwan sits on top of an area where the Earth's crust is thin. Deep underground, there are pockets of hot rock. When rainwater seeps down and touches that rock, it heats up. Then it bubbles back up to the surface, sometimes still steaming. Some hot springs are warm like a bath; others are almost boiling.
In a hot spring bath, you sit in a pool of warm water with the cool air on your face. Many of the springs are outdoors, surrounded by trees. In autumn, leaves drift down onto the water as you soak. People say it is one of the most peaceful things you can do.
Hot spring water often has minerals in it - tiny bits of rock and salt - that some people believe are good for your skin. Each hot spring has a slightly different mix. Some smell a bit like rotten eggs because of a mineral called sulphur. Others have water that looks white, or pale blue.
Hot springs are also part of the wildlife story. At a place called Jigokudani in Japan, monkeys bathe in hot springs. In Taiwan, the Formosan macaques live near the springs too, although they don't usually take baths. They just enjoy the warmth around them on cold mountain mornings.