A cave located in Steamboat Springs nestled at the foot of an in-town ski hill is unlike any other in Colorado and has some unique residents that have elevated it to National Natural Landmark status. The Sulphur Cave is full of toxic gases deadly to humans (hydrogen sulfide & carbon dioxide) but perfect living conditions for the rare blood red worms. About 25 feet deep and 200 feet long, the cave has very low ceilings that drip acid so strong it will burn through your clothes. Water from Steamboat’s hot springs flows naturally into the cave entrance forming a small stream along its muddy, soupy floor.
Two interesting things about this: The resident expert on the worms studies them with using SCBA (Self-Contained Breathing Apparatus). Also in 1962 an Italian exchange student who entered the cave with only an oxygen mask came out convulsing and falling in and out of consciousness with “wild eyes.”
Here’s more on the wormies: