Pamukkale, meaning "cotton castle" in Turkish, is a natural site in Denizli Province in southwestern Turkey. The area is famous for a carbonate mineral left by the flowing of thermal spring water. It is located in Turkey's Inner Aegean region, in the River Menderes valley, which has a temperate climate for most of the year.
Pamukkale's terraces are made of travertine, a sedimentary rock deposited by mineral water from the hot springs. In this area, there are 17 hot springs with temperatures ranging from 35 °C to 100 °C. The water that emerges from the spring is transported 320 meters to the head of the travertine terraces and deposits calcium carbonate on sections 60 to 70 meters long covering an expanse of 24 meters to 30 meters. When the water, supersaturated with calcium carbonate, reaches the surface, carbon dioxide de-gasses from it, and calcium carbonate is deposited. Calcium carbonate is deposited by the water as a soft gel which eventually crystallizes into travertine.
For thousands of years, these minerals have formed and are known for their healing properties. The Turks often say that bathing in these pools will heal certain illnesses including chronic disorders, digestive problems, eye and skin diseases, and many more. So, Pamukkale has been a popular spa attraction since ancient times. At a glance, the pools look like they may be cold because it looks so much like snow. However, they are warm and super relaxing.
In addition to being known for its brilliant white travertine terraces and warm thermal pools, it’s also the site of the well-preserved ruins of the Greek-Roman city Hierapolis, which contains one of the oldest theaters in the world. The ancient Greek city of Hierapolis was built on top of the travertine formation which is in total about 2,700 m long, 600 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. This area has been drawing visitors to its thermal springs since the time of classical antiquity.
Pamukkale is recognized as a World Heritage Site together with Hierapolis. Hierapolis-Pamukkale was made a World Heritage Site in 1988. It is a tourist attraction because of its status and its natural beauty.
According to Wikipedia