Pamukkale Denizli Province, Turkey

Pamukkale, meaning /cotton castle/ in Turkish, is a natural site in Denizli Province in southwestern Turkey. The city contains hot springs and travertines, terraces of carbonate minerals left by the flowing water. It is located in Inner Aegean region of Turkey, in the River Menderes valley, which has a temperate climate for most of the year.

The ancient Greco-Roman and Byzantine city of Hierapolis was built on top of the White Castle which is in total about 2700 meters long, 600 meters wide and 160 meters high. It can be seen from the hills on the opposite side of the valley in the town of Denizli, 20 km away. People have bathed in its pools for thousands of years. Wearing shoes in the water is prohibited to protect the deposits. The terraces are made of travertine, a sedimentary rock deposited by water from the hot springs. In this area, there are 17 hot water springs in which the temperature ranges from 35 °C (95 °F) to 100 °C (212 °F). The water that emerges from the spring is transported 320 meters to the head of the travertine terraces and deposits calcium carbonate on a section 60 to 70 meters long covering an expanse of 240 meters to 300 meters. When the water, supersaturated with calcium carbonate, reaches the surface, carbon dioxide degasses from it, and calcium carbonate is deposited. The depositing continues until the carbon dioxide in the water balances the carbon dioxide in the air. Calcium carbonate is deposited by the water as a soft jelly, but this eventually hardens into travertine.

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