Pamukkale, meaning "cotton castle" in Turkish, is a natural site and attraction in south-western Turkey in the Denizli Province. The ancient city of Hierapolis was built on top of the white "castle" which is in total about 2700 meters long and 160m high. It can be seen from a great distance, eg. when driving down the hills on the opposite side of the valley to the town of Denizli, which is 20 km away.
Pamukkale is located in the Inner Aegean region, in the Maeander River valley, which enjoys a temperate climate over the greater part of the year. The tectonic movements that took place in the fault depression of the Menderes river basin did not only cause frequent earthwuakes, but also gave rise to the emergence of a number of very hot springs, and it is the water from one of these springs, with its large mineral content, chalk in particular. Apart of some radioactive material, the water contains large amounts of hydrogen carbonate and calcium, which leads to the precipitation of calcium carbonate. The effect of this natural phenomenon leaves thick white layers of limestone and travertine cascading down the mountain slope, making the area look like a fortress of cotton or a frozen waterfall.