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. The ancient Greek city of Hierapolis was built on top of the travertine formation which is in total about long, wide and 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. The Turkish name refers to the surface of the shimmering, snow-white limestone, shaped over millennia by calcite-rich springs. Dripping slowly down the mountainside, mineral-rich waters collect in and cascade down the mineral terraces, into pools below. It was added as a UNESCO World Heritage Site in 1988 along with Hierapolis. Geology 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 to . The water that emerges from the spring is transported to the head of the travertine terraces and deposits calcium carbonate on a section long covering an expanse of to . 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. Archaeology There are only a few historical facts known about the origin of the city. No traces of the presence of Hittites or Persians have been found. The Phrygians built a temple, probably in the first half of the 7th century BC. This temple, originally used by the citizens of the nearby town of Laodicea, would later form the centre of Hierapolis. Hierapolis was founded as a thermal spa early in the 2nd century BC within the sphere of the Seleucid Empire. Antiochus the Great sent 2,000 Jewish families to Lydia and Phrygia from Babylon and Mesopotamia, later joined by more from Judea. The Jewish congregation grew in Hierapolis and has been estimated as high as 50,000 in 62 BC. Hierapolis became a healing centre where doctors used the thermal springs as a treatment for their