Ploutonion at Hierapolis

Lore & Background

The Ploutonion was a small cave with a fenced entrance and stairs descending into a chamber, behind which a deep cleft released fast-flowing hot water and a sharp-smelling, suffocating gas. Ancient writers including Strabo, Cassius Dio, and Damascius described the site. Strabo noted that any animal passing inside died instantly, and he personally threw in sparrows that immediately perished. The gas, heavier than air, settled in hollows, creating an enclosed area of 2,000 square meters in front of the entrance that was lethal to anyone who entered.

Ritual animal sacrifices were common: animals were thrown into the cave and pulled back with ropes. The castrated priests of Cybele, known as the Galli, would descend into the Ploutonion, crawling to pockets of oxygen or holding their breath, then emerge unharmed, convincing onlookers they had divine protection. Visitors could buy birds and other animals from the priests to test the deadly nature of the area, and for a fee could consult the oracle of Pluto, generating considerable income for the temple.

The entrance was closed off during Christian times. Archaeological evidence indicates the site was fully functional until the 4th century AD, with sporadic visitation for the next two centuries. The temple was destroyed in the 6th century AD by earthquakes.

Reader's Guide

The Ploutonion at Hierapolis holds significance as a rare archaeological example of a ploutonion—a site where ancient peoples directly linked geological phenomena with religious belief. The toxic carbon dioxide emissions, caused by underground seismic activity, were interpreted as the breath of Pluto, god of the underworld, making the cave a literal gateway to Hades. This connection was reinforced by the site's location on a seismic fault, recognized in 1998 by geologist Luigi Piccardi, who noted that both the Ploutonion and the nearby Apollo's Oracle were deliberately built on this fault line.

The site's legacy extends to its role in ancient ritual practice. The priests' ability to survive the gas—by exploiting the fact that carbon dioxide settles near the ground—was seen as miraculous, reinforcing the temple's authority and generating revenue through oracle consultations and animal sales. The discovery and restoration work by Italian archaeologists, including Francesco D'Andria in 2013, have preserved the site for study. A replica of the marble statue of Hades and Cerberus, known to have been present in ancient times, has been restored to its original place as part of a restoration project. The Ploutonion remains a key site for understanding how ancient cultures integrated natural hazards into their spiritual worldview.

Did You Know?

• The Ploutonion was discovered in 1965 by Italian archaeologists, who published reports throughout the decade.
• In 1998, geologist Luigi Piccardi recognized that the site was built on a seismic fault, linking it to the Gateway of Hades.
• The ancient historian Strabo wrote that he threw sparrows into the cave and they 'immediately breathed their last and fell.'
• A replica of the marble statue of Hades and Cerberus has been restored to its original place at the site.