Found in 1986 by Cristian Lascu during construction work a few kilometres from the Black Sea, and it had been sealed off from the surface for about 5.5 million years. Everything living in it runs on chemosynthesis: no sunlight reaches it and nothing depends on any that does, the whole food web built on hydrogen sulfide and carbon dioxide. Fifty-seven animal species live down there and thirty-seven of them exist nowhere else on Earth. The air is not survivable without gear, 7 to 10 percent oxygen against 21 outside, 2 to 3.5 percent carbon dioxide against 0.04, plus methane, hydrogen sulfide and ammonia. You cannot visit. Access is limited to a handful of researchers a year to keep the ecosystem intact, and that limit is the right call. It is here because it is one of the strangest places on the planet and worth knowing exists. Mangalia, Constanța County.
Mangalia, Romania
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