Pamukkale means "cotton castle" in Turkish. Snow-white travertine terraces filled with turquoise water cascade down the mountainside. This is a geological wonder, thermal spa, and UNESCO World Heritage Site all in one place.

How the Terraces Formed

Hot springs rich in calcium emerge at the surface and flow down the slope. When exposed to air, carbon dioxide escapes, calcium carbonate precipitates, and travertine forms—a white porous limestone.

This process has continued for millennia. The terraces grow a few millimeters each year. What you see is the result of hundreds of thousands of years...