In the south-east of Romania, in Constanța county close to the Black Sea and the Bulgarian border, there lies a barren featureless plain. The desolate field is completely unremarkable, except for one thing.

Below it lies a cave that has remained isolated for 5.5 million years. While our ape-like ancestors were coming down from the trees and evolving into modern humans, the inhabitants of this cave were cut off from the rest of the planet.

Despite a complete absence of light and a poisonous atmosphere, the cave is crawling with life. There are unique spiders, scorpions, woodlice and centipedes, many never before seen by humans, and all of them owe their lives to a strange floating mat of bacteria.

In 1986, workers in communist Romania were testing the ground to see if it was suitable for a power plant, when they stumbled across the Movile Cave. Romanian scientist Cristian Lascu was the first to make the dangerous descent. (...)

Some interesting takeaways: (credit : https://news.ycombinator.com/item?id=11683260 )

  • The cave is called "Movile".
  • 3 species of spider, a centipede, 4 species of isopod (the group that includes woodlice), a leech never seen anywhere else in the world, and an unusual-looking insect called a waterscorpion
  • Movile's only snail [probably the only snail species] suggested that it has been down there for just over 2 million years.
  • Many animals are born without eyes, which would be useless in the dark. Almost all are translucent as they have lost pigment in their skin.
  • The cave seems to have no contact with the surface; Chernobyl accident had released lots of radioactive metals, which had found their way into the soils and lakes surrounding Movile Cave. However, a 1996 study found no traces of them inside the cave.
  • The ecosystem seems to be supported by chemosynthesis; bacteria oxidise methane, sulphide and ammonia, generating energy and organic matter.

http://www.bbc.com/earth/story/20150904-the-bizarre-beasts-living-in-romanias-poison-cave