Pamukkale and Hierapolis

Pamukkale and Hierapolis form a joint UNESCO World Heritage Site in Denizli province, southwestern Turkey, combining a remarkable natural geological formation with the extensive ruins of a Greco-Roman spa city. Pamukkale — meaning cotton castle in Turkish — consists of a cascading hillside of brilliant-white calcium carbonate (travertine) terraces formed by thermal spring water rich in dissolved calcium bicarbonate. As the water cools and loses carbon dioxide upon emerging from the earth at around 35°C, calcium carbonate precipitates and gradually builds the terraced pools over millennia. The terraces extend approximately 2.7 km across the hillside and rise roughly 160 metres above the Denizli plain below, creating a landscape unlike any other in Turkey. At the crest of the travertine hillside sits the ancient city of Hierapolis, founded as a Greco-Roman colony around 190 BC under the Seleucid king and later absorbed into the Roman Empire in 133 BC. The city's therapeutic hot springs attracted wealthy visitors and permanent settlers from across the Roman world. Hierapolis reached its greatest prosperity during the 2nd and 3rd centuries AD when major construction programmes expanded the city's baths, colonnaded streets, and public monuments. The city is believed to have been an early centre of Christianity: the Apostle Philip is traditionally associated with Hierapolis and a 5th-century martyrium over his supposed burial site is preserved on the eastern ridge. The archaeological zone preserves a monumental colonnaded street (the Plateia), a well-maintained Roman theatre seating 10,000 spectators with its sculpted stage building largely intact, the vast Necropolis extending along the northern city walls (one of the largest Roman burial grounds in the world), and a Roman bathing complex now housing the Hierapolis Archaeological Museum. The Antique Pool (Cleopatra's Pool) — a thermal swimming pool scattered with fragments of fallen Roman columns — allows visitors to swim among submerged antiquities for an additional fee. Visitors must walk barefoot through the thermal pools on the white travertine; shoes are required in the archaeological area above.