Hierapolis-Pamukkale

HIERAPOLIS-PAMUKKALE Denizli Province, Turkey · Ongoing geological / 190 BCE onwards · Graeco-Roman and geological AT-RISK

SITE AT A GLANCE Location: Denizli Province, Aegean Turkey Country: Turkey Region: West Asia / Eastern Mediterranean Coordinates: 37.9200° N, 29.1200° E Type: Natural and Built Heritage Sub-types: Geological Landscape, Graeco-Roman City, Archaeological Site Period: Travertine formation over ~400,000 years; Hierapolis founded 190 BCE; Roman peak 2nd–3rd century CE Risk Level: At-Risk Risks: Tourist footfall on travertine, Water diversion, Previous hotel damage, Earthquake vulnerability, Climate change UNESCO Status: Inscribed 1988

3D DOCUMENTATION A photogrammetric scan of the Hierapolis Theatre, one of the best-preserved Roman theatres in Turkey, produced by Arqueomodel3D (Juan Brualla, free access) is available on Sketchfab. The Italian Archaeological Mission in Hierapolis (MAIER) publishes excavation reports at maier.it, including the discovery and analysis of the Plutonium. Europeana hosts digitised Roman records relating to the site. The UNESCO World Heritage dossier provides authoritative geological and archaeological documentation. Sketchfab — Hierapolis Theatre photogrammetry (Arqueomodel3D, free): https://sketchfab.com/3d-models/hierapolis-theatre-turkey-98b7346d378e4bdf98309596dc7c4761 Italian Archaeological Mission in Hierapolis: https://www.maier.it/ UNESCO dossier: https://whc.unesco.org/en/list/485

SITE DESCRIPTION Each second, approximately 250 litres of water emerge from the hillside at 35°C, saturated with calcium bicarbonate. As carbon dioxide escapes into the air, calcium carbonate precipitates as calcite crystals — white, crystalline, building at approximately 1 to 2 millimetres per year — and the process that has been running for at least 400,000 years continues. The Ottoman traveller Evliya Çelebi described the result in the 17th century: it is as though the gods poured boiling milk down the mountainside and it froze where it fell. Pools of turquoise water sit behind rimstone dams of dazzling white. The terraces cascade 200 metres down the hillside. The formations look like snow that never melts, or a glacier that formed in the Aegean summer. They are, in geological terms, alive: continuously growing where water flows, deteriorating where it does not. Above the terraces, Hierapolis (Sacred City) was founded by the Pergamene king Eumenes II around 190 BCE and reached its greatest prosperity under Roman imperial patronage in the 2nd and 3rd centuries CE. The theatre, seating approximately 12,000 spectators, is among the best-preserved in Turkey. The necropoleis surrounding the city contain over 1,200 tombs from the Hellenistic through Byzantine periods.

HISTORICAL SIGNIFICANCE The thermal springs were understood in antiquity as sacred and healing — their warmth associated with the divine, their therapeutic properties attracting the sick and wealthy from across the Mediterranean world. Hierapolis became one of the most prosperous spa cities in Asia Minor, and the belief that dying near the sacred waters eased the transition to the afterlife drove the development of one of the largest concentrations of Graeco-Roman funerary architecture in the world. The Plutonium is the most remarkable feature of Hierapolis's religious life and the one that ancient writers found most worth recording: a cave entrance understood as a literal gateway to the underworld, emitting deadly vapours that killed animals led to its entrance while apparently immune priests of Cybele survived. The cave was rediscovered by archaeologists in 2013. Measurements confirmed lethal carbon dioxide concentrations produced by volcanic activity beneath the site. Ancient priests were protected by a phenomenon they could observe but not fully explain: CO₂ concentrations that pool at low levels kill shorter people while taller priests, standing upright, breathe above the lethal layer. The ancient account is scientifically accurate in every observable detail.

THE STORY OF THE SITE

c. 400,000 Years Ago: The Travertine Begins Thermal springs begin depositing calcium carbonate on the hillside above what will become the Lycus Valley. The process that will eventually create Pamukkale — and attract Graeco-Roman settlers to build a city above it — runs continuously from this point to the present, at approximately 1 to 2 millimetres per year.

190 BCE: Hierapolis Founded The Pergamene king Eumenes II establishes Hierapolis above the thermal springs, beginning two millennia of urban settlement exploiting the site's therapeutic and sacred properties. The city grows steadily through the Hellenistic period, attracting the sick and the wealthy.

17 CE: Earthquake and Rebuilding A severe earthquake destroys much of the early Hierapolis. The city is rebuilt with Roman financial support, beginning the period of greatest prosperity. The theatre, baths, and major public buildings date from this Roman reconstruction.

2nd to 3rd Century CE: Roman Peak Hierapolis reaches its greatest prosperity under Roman imperial patronage. The theatre is built to seat 12,000 spectators. The colonnaded street, the nymphaeum, and the major bath complexes are constructed. The necropoleis expand. The Plutonium continues to operate as a sacred site.

1988 to Late 20th Century: UNESCO and Hotel Damage UNESCO inscription in 1988. Hotels are built directly on the travertine during the late 20th century, causing severe damage to the formations. Swimming pools are constructed in the terraces. The hotels are subsequently demolished and the travertine begins its slow recovery. Portions that were white decades ago remain brown and biologically colonised. Visitors are now required to remove footwear before walking on the terraces.

2013: The Plutonium Rediscovered Italian archaeologists excavating adjacent to the Temple of Apollo identify and excavate the Plutonium — the ancient cave entrance believed to be a gateway to the underworld. Measurements confirm lethal carbon dioxide emissions from volcanic activity beneath the site, precisely as ancient writers described. The ancient account of animal deaths and priestly survival is explained for the first time in two thousand years.

THREATS AND RISK ASSESSMENT The Travertine as a Living System The travertine terraces are not a static monument. They are a living geological feature that grows where water flows and deteriorates where it does not. Water management is therefore the central conservation challenge: the volume of spring water reaching the terraces must be maintained, the areas where tourists walk must be channelled to allow the formations to continue building, and the diversion of spring water for hotel pools and other non-touristic uses must be controlled. Tourist footfall, even barefoot as now required, causes measurable surface damage to the softer rimstone formations.

Previous Damage and Recovery The hotels built on the travertine in the late 20th century caused damage that will take decades to heal. Sections of the terraces that were photographed in their pristine white state forty years ago are now brown with biological colonisation and structurally compromised. The recovery is real but slow, and it requires the sustained management of water distribution across the terraces that existing infrastructure provides only partially.

RESEARCH AND SCHOLARLY CONTEXT The Italian Archaeological Mission in Hierapolis (MAIER) is the primary research institution at the site, having conducted systematic excavation and published detailed reports for several decades. Their 2013 identification and analysis of the Plutonium — the ancient gateway to the underworld — is the most significant recent discovery at the site and has been published in peer-reviewed journals. The photogrammetric scan of the theatre on Sketchfab provides accessible documentation for researchers and educators. The UNESCO World Heritage dossier covers both the geological and archaeological dimensions of the site in authoritative detail.

IF NOTHING CHANGES The travertine terraces will continue to heal from the hotel damage of the late 20th century, more slowly than optimists hope and faster than pessimists fear, as long as the spring water continues to flow across them in adequate volume. The threat is less from tourism per se than from the diversion of spring water for commercial uses that reduce the flow available for terrace regeneration. If the flow is maintained and visitor management continued, the terraces will slowly recover. If the flow is reduced, they will not. The Plutonium, now protected by a fence that keeps tourists at a distance that ancient priests did not maintain, continues to emit its lethal carbon dioxide into an atmosphere that tourists breathe at the margins of the site. It has been doing this for millions of years and will continue regardless of what humans choose to do about the rest.