Costa Rica’s eerie Cueva de la Muerte, or “Cave of Death,” hides an invisible danger along its floor: a remarkably stable pool of carbon dioxide that can reach nearly 100% concentration. Because CO₂ is heavier than air, it settles low in the cave, creating a deadly zone for small animals that wander inside. In the video, the danger becomes strikingly clear when a flame is lowered toward the cave floor and suddenly goes out, showing just how little oxygen is present in the gas-filled layer.
WATCH:
Costa Rica’s Cave of Death (Cueva de la Muerte) is a pool of carbon dioxide on the floor, which is remarkably stable, and nearly 100% CO₂: fatal to every animal that enters the cave. See how a flame can’t burn. [📹 MichaelCon] https://t.co/e08UsdsOm3
— Massimo (@Rainmaker1973) October 5, 2026