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