Sunset over the travertine terraces at Pamukkale, Turkey.
"Pamukkale, meaning "cotton castle" in Turkish, is a natural site in Denizli Province in south-western Turkey. The city contains hot springs and travertines, terraces of carbonate minerals left by the flowing 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 city of Hierapolis was built on top of the white "castle" which is in total about 2,700 metres (8,860 ft) long, 600 m (1,970 ft) wide and 160 m (525 ft) high."