Pamukkale, meaning "cotton castle" in Turkish, is a natural site in Denizli Province in south-western Turkey. The city contains hot springs and travertines, terraces of carbonate minerals. It is located in Turkey's Inner Aegean region, in the River Menderes valley, which has a temperate climate for most of the year.

The ancient city of Hierapolis was built on top of the white "castle" which is in total about 2,700 metres long, 600 m wide and 160 m high. It can be seen from the hills on the opposite side of the valley in the town of Denizli, 20 km away.

Tourism is and has been a major industry. People have bathed in its pools for thousands of years.

The calcareous water runs over the greater number of terraces on a slope. The warm water (35 °) leaves calcium carbonate behind and so are thick packets of limestone are formed along the terraces. This gives the slope a special view: it looks like a castle of cotton or a frozen waterfall. However, because of the large number of tourists is the process of calcification is affected. Wearing shoes in the water is prohibited to protect the deposits.

Pamukkale is a tourist attraction. It is recognized as a World Heritage Sites together with Hierapolis.

The underground volcanic activity which causes the hot springs also forced carbon dioxide into a cave, which was called the Plutonium meaning place of the god, Pluto. This cave was used for religious purposes by priests of Cybele, who found ways to appear immune to the suffocating gas.

Tadpoles can be found in the pools.