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 2,700 m 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, 20km 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.