How a Roman ‘Gate to Hell’ Actually Worked


Is it possible to walk through the gates of hell and live? Ancient Romans thought so, and they staged elaborate sacrifices at what they believed were entrances to the underworld. How did that work? (Science)

Learn a little about Ancient Rome, and why “gates to hell” are still deadly today.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit, including today’s MapMaker Interactive map.

The gate to hell in Hierapolis is a stone doorway leading to a small cave-like grotto.
Photographs by Ömerulusoy, courtesy Wikimedia. CC-BY-3.0
In the grotto, watch out for those mists.
Photographs by Ömerulusoy, courtesy Wikimedia. CC-BY-3.0

Discussion Ideas




  • If the concentrations of carbon dioxide were enough to kill a person in a minute, how did the priests at Hierapolis avoid death?
    • They were taller than the sacrificial animals. The carbon dioxide “lake” was a little more than a foot deep. “Sacrificial animals were not tall enough to keep their heads fully clear of the CO2 lake, and as they became dizzy, their heads would have dropped even lower, exposing them to higher CO2 concentrations and leading to death by asphyxiation. The priests, however, were tall enough to keep their heads above the dangerous gasses, and may have even stood on stones to add to their height.”


  • Is the plutonium at Hierapolis still emitting its deadly “breath” today, or has volcanic activity slowed in the intervening millennia?


  • This research is so, so cool. What makes it exciting for multidisciplinary scholars?
    • The research “proves the veracity of ancient sources and helps explain not only why people could enter, but also why animals would die.” It “strongly corroborates that at least in the case of Hierapolis, ancient writers like Strabo or Plinius described a mystic phenomenon very exactly without much exaggeration.”
      • This makes it of interest to geologists, classicists, chemists, historians, and, of course, geographers.



Science: This Roman ‘gate to hell’ killed its victims with a cloud of deadly carbon dioxide

Nat Geo: Plutonium at Hierapolis map

Nat Geo: Ancient Rome

Nat Geo: Volcanic Gas Kills Thousands article

UNESCO World Heritage Center: Hierapolis-Pamukkale

(extra credit! paywalled) Archaeological and Anthropological Sciences: Deadly CO2 gases in the Plutonium of Hierapolis (Denizli, Turkey)

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