A brilliant white staircase of travertine terraces in Denizli Province, southwestern Turkey, formed as calcium-carbonate-rich spring water flows down the hillside. Above the terraces lie the ruins of Hierapolis, an ancient Roman spa city, and visitors can bathe among submerged ancient marble columns in the Antique Pool, legendarily linked to a visit by Cleopatra. The site is a UNESCO World Heritage Site, with spring water around 35°C.