Movile Cave

Movile Cave lies near Mangalia in Constanta County, Romania, a few kilometers from the Black Sea coast, and was discovered in 1986 during construction work. It is a limestone karst cave shaped by acidic groundwater dissolving carbonate rock over millions of years, but its passages, only about 200 meters of interconnected galleries, were sealed off from the surface for roughly 5.5 million years, cutting the cave off from sunlight entirely. Its air holds only seven to ten percent oxygen against the twenty one percent found outside, alongside dangerous concentrations of hydrogen sulfide, carbon dioxide and methane, conditions that have produced an ecosystem powered entirely by chemosynthesis rather than photosynthesis. Fifty seven animal species live in the cave, thirty seven of them found nowhere else on Earth, making Movile one of the most isolated and scientifically significant cave ecosystems known.