Pamukkale

The warm water carries something hidden inside it. It is a white mineral, too tiny to see.

When the water flows over the hill, it leaves the mineral behind. At first it is soft, like jelly. Then it slowly turns into hard white rock.

The water at Pamukkale comes up warm from underground, between 35 and 60 degrees Celsius at its source, the European Geosciences Union says. It carries a lot of dissolved calcium carbonate, the same mineral found in chalk and limestone.

When the water meets the air and spreads out over the slope, it leaves calcium carbonate behind. The new layer starts out soft, like a jelly, and slowly hardens into rock. This rock is called travertine. Britannica describes travertine as a dense, banded kind of limestone that forms from river and spring water. Layer after layer, the water has been building Pamukkale's terraces for about 400,000 years.

Travertine, Britannica explains, is a dense, banded rock of calcite (CaCO₃), a light-colored variety of limestone deposited from spring and river waters; the Mammoth Hot Springs in Yellowstone are another place where it is actively forming. At Pamukkale, the European Geosciences Union reports, the water leaves its source at 35–60 °C carrying a high concentration of calcium carbonate, and on contact with air it deposits the mineral, at first as a soft gel that hardens over time.

The same source estimates that about 500 mg of calcium carbonate is deposited for every liter of water, and that the travertines have been forming for the last 400,000 years. The rate depends on the weather, the air temperature and how long water flows from the spring.

Long ago, people built a town on top of the white hill.

They used the warm water for baths. They washed wool in it, too. Little canals carried the water to farms and villages.

People have used Pamukkale's warm water for more than 2,000 years. UNESCO explains that the springs fed the baths of the ancient town of Hierapolis, with big hot basins and swimming pools. The hot springs were also used for scouring and drying wool.

People dug a whole system of canals to carry the thermal water to nearby villages and fields. UNESCO says this water system stretches about 70 kilometers to the northwest and westward along the valley of the Menderes River. Today, special areas let visitors bathe in the hot springs, while the white terraces themselves are protected.

UNESCO treats the combination of the natural formations and an elaborate canal system as exceptional: the springs supplied a hydraulic network extending some 70 km northwest to Alaşehir and westward along the Menderes valley, carrying thermal water to villages and fields. In Hierapolis the water fed immense hot basins and swimming pools, and the springs were also used for scouring and drying wool.

That long human use continues today and brings pressure. UNESCO identifies high numbers of international tourists, an important economic resource for the region, as the main threat to the property's integrity, especially at the small lake around the ancient civic agora where visitors swim among fallen columns, causing biological pollution and erosion of the Roman marble.

On top of the hill are the ruins of an old town called Hierapolis.

You can see a big stone theater, old baths and a long street. Earthquakes knocked the town down many times.

Hierapolis was founded in the 2nd century BCE by a king of Pergamon, Türkiye's Ministry of Culture and Tourism says. It later came under Rome and grew into an important town. Earthquakes destroyed it again and again. After a great earthquake in the year 60, the town was rebuilt in a neat grid of streets, with a main street about one kilometer long lined with shops and workshops.

Archaeologists have uncovered baths, a big theater, a monumental gateway, churches and huge cemeteries. An Italian team has been digging and restoring here since 1957. After another earthquake in the 1300s, the town was abandoned.

Türkiye's Ministry of Culture and Tourism dates the foundation to Eumenes II, king of Pergamon, in the 2nd century BCE; UNESCO says Hierapolis passed to Rome in 133 BCE, was destroyed by an earthquake in 60 CE and rebuilt, and reached its height in the 2nd and 3rd centuries CE. The rebuilt town followed a Roman grid plan around a main colonnaded street of about 1 km with two monumental gates. Surviving remains include baths, a monumental arch, a nymphaeum, the theater from the time of Severus and necropolises that UNESCO says extend over 2 km, the largest in southwest Anatolia according to the ministry.

From the 4th century Hierapolis was a bishopric with several churches, built between the 4th and 6th centuries. It was damaged again in the 7th century, was a small town under the Seljuk Sultanate in the 13th century and was abandoned after an earthquake in the 14th. An Italian excavation team has worked here since 1957, restoring monuments by anastylosis (rebuilding with the original pieces).

The white pools are very delicate.

Visitors stay on the paths. They swim only in the places that are allowed. Walk slowly, because wet rock can be slippery.

Pamukkale is easily damaged. In the past, hotels stood on the site and a road crossed the terraces. UNESCO reports that the hotels and buildings around the thermal pool have been removed, the road has been closed and private cars are not allowed in, except in emergencies. Public transport carries visitors instead.

Visitors follow marked routes with information panels and are kept off the travertine terraces so the water can keep flowing over them. There are special places where bathing in the hot springs is allowed. Follow the signs and the staff, and remember that wet stone can be slippery.

UNESCO records a series of management changes: the site was registered as a first-degree natural and archaeological site in 1980, and in 1990 about 66 km² was declared a special protected area. Hotel buildings on the site and structures around the thermal pool were removed, the road through the southeastern terraces was closed, private vehicles are banned except for emergencies, public transport is provided and tourist facilities are kept at the edge of the monumental zone, with visitor centers at the north and south entrances.

Access to the travertine terraces is prohibited to sustain the water flow and preserve their color and structure, and designated areas are provided for bathing. Visitors protect the site by staying on marked routes, bathing only where permitted and taking care on wet, slippery surfaces.