Pamukkale is a white hillside of terraced pools in southwestern Türkiye, in Denizli province, still being built by hot springs that lay down fresh limestone as they cool, with the Greco-Roman spa city of Hierapolis on the ridge above it, and it is walked barefoot, with warm mineral water running over the feet down the snow-white steps. The name means cotton castle, and the terraces are travertine, calcium carbonate dropped by water that comes out of the ground at 35 degrees and spreads over the slope in a sheet, so that the hill has grown for thousands of years and its face is 160 metres high and two and a half kilometres long; shoes come off at the gate to protect the surface, and the walk goes down the wet white channel from the top with the pools of blue water in their scalloped basins on either side. The kings of Pergamon founded Hierapolis on the ridge beside the healing waters in the second century BC, and the Romans made it a spa city whose theatre, baths and colonnaded street still stand, with the tomb of the apostle Philip on the hill.
The Antique Pool, the one everyone calls Cleopatra's, stays warm all year and is strewn with marble columns and Corinthian capitals that slid underwater when a seventh-century earthquake brought down the Temple of Apollo above it, so that swimmers float over toppled marble rather than around it. Beside the temple a cave breathes out carbon dioxide dense enough to kill, the ancient Ploutonion, a gate to the underworld where priests led animals in to die before the crowd and came out alive by holding their breath. One of the largest ancient cemeteries in Anatolia spreads around the edges of the city, with over a thousand tombs, and balloons rise at dawn to show that the white face is the cut edge of a whole plateau of travertine. Pamukkale is a hill that water is still building, and a city was built to bathe in it.