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Steamboat’s toxic cave is home to weird worms, crystal-forming bacteria and now, possibly, a National Natural Landmark

By Eleanor C. Hasenbeck
ehasenbeck@SteamboatPilot.com
Snottites hang as gypsum crystals form on the walls of the Sulphur Cave.
Courtesy city of Steamboat Springs

Editor’s note: Entry into the Sulphur Cave is prohibited and can result in death or harm to your health. Members of the public should not enter the cave.

STEAMBOAT SPRINGS — The air inside is deadly. It has one-of-a-kind worms that survive in a mix of elements that is toxic to humans. Gooey bacteria drip from the ceiling, as crystals of gypsum are slowly forming, and it’s right under our feet. 

The Sulphur Cave at Howelsen Hill is under consideration for a National Natural Landmark through the National Park Service. At Tuesday’s Steamboat Springs City Council meeting, city staff will seek direction from City Council as to whether they should pursue the designation for the unique cave.



There are a multitude of features that make the cave distinct.

It’s likely the first cave documented in Colorado, described in 1843 by Thomas Jefferson Farnham in Travels in the Great Western Prairies.

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Then there’s the atmosphere. Breathing in the mix of hydrogen sulfide, carbon dioxide and carbon monoxide in the cave can kill a person. Even one or two breaths could knock you out, Fred Luiszer, a University of Colorado scientist who specializes in caves told Steamboat Pilot & Today in 2008.

Read the full story at the Steamboat Pilot.


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