Pamukkale (cotton castle) , Turkey.

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Pamukkale, meaning "cotton castle" in Turkish, is a natural site and attraction in south-western Turkey in the Denizli Province. Pamukkale is located in Turkey's Inner Aegean region, in the River Menderes valley, which enjoys a temperate climate over the greater part of the year.

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 the hills on the opposite side of the valley in the town of Denizli, 20 km away.

@Wikipedia