A volcano does not always look like the tall pointed cone you might draw in a picture. Sulphur Springs is a caldera — that means the top of the ancient volcano collapsed inward long ago, leaving a wide, flat-bottomed bowl. Now a road runs straight into that bowl, and visitors can walk among the steaming vents and watch the mud pop and bubble.
The water and mud here are naturally hot because they are heated by the volcanic rocks deep underground. The minerals in the water give it a very unusual colour — sometimes white, sometimes grey, sometimes tinged with orange. The air smells strongly of rotten eggs because of the sulphur gas, which is quite natural and not harmful on a short visit.
People have been visiting Sulphur Springs for a very long time because the warm, mineral-rich water is said to be good for skin. Visitors can bathe in specially prepared pools nearby. Scientists visit too, because watching how the volcanic gases and water behave helps them understand what is happening deep inside the Earth.