Movile Cave, known for its isolated ecosystem, is in Romania.
The cave is located near Mangalia in Constanța County, close to Romania’s Black Sea coast. It was discovered in 1986 during construction work, when workers opened an artificial entrance into a sealed underground environment.
Movile is famous because its food web is based on chemosynthesis rather than sunlight. Sulfur-oxidizing and methane-using microorganisms form the foundation of the ecosystem, allowing invertebrates to survive in water and air with very little oxygen and unusually high levels of carbon dioxide, hydrogen sulfide, and ammonia.
The cave’s isolation is often described as lasting about 5.5 million years, although individual species arrived at different times. Researchers have recorded dozens of animal species, many endemic to the cave. Access is tightly restricted because the atmosphere is hazardous and the ecosystem is highly sensitive to outside disturbance. It is not in neighboring Bulgaria, Hungary, or Serbia.