Travertine terraces of Pamukkale, Turkey

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Heavenly hot springs. Pamukkale, Turkey

The stunning travertine terraces and hot pools of Pamukkale, Turkey, have dazzled visitors since at least the end of the 2nd century BCE, with the founding of the Greco-Roman thermal spa of Hierapolis. Since then, people have enjoyed a relaxing soak in the 97-degree Fahrenheit water, claiming curative powers for many ailments.

It makes sense that Pamukkale is also known as the 'Cotton Palace,' in a nod to the fluffy-looking white formations that cover the hillside. That 'cotton' is travertine, a soft limestone that is formed over centuries as calcite-laden water drops from springs in a cliff high above. Here it's a stunning white, but travertine can be found in many different colors, ranging from gray to gold.

Pamukkale, with its travertine terraces, and the ancient ruins of Hierapolis are so unique that they were named a UNESCO World Heritage Site. To protect the pools, authorities now limit the number of bathers, so you may not be allowed to take a dip. But there's plenty more to marvel at here. Walk around the ruins of the theater, necropolis, ancient temples, and bath houses in Hierapolis. You'll be in good company: The hot springs and Hierapolis draw more than 2 million visitors a year, making Pamukkale one of Turkey's most visited attractions.