Eighteen metres under a field in Romania sits a cave whose air no human can breathe for long — no light, a fraction of the oxygen up top, thick with the rotten-egg reek of hydrogen sulphide — and yet it holds dozens of pale, eyeless species that have fed on poison in total darkness for as long as five and a half million years

Eighteen metres under a field in Romania sits a cave whose air no human can breathe for long — no light, a fraction of the oxygen up top, thick with the rotten-egg reek of hydrogen sulphide — and yet it holds dozens of pale, eyeless species that have fed on poison in total darkness for as long as five and a half million years

Eighteen metres below a field on the outskirts of Mangalia in south-eastern Romania, two kilometres from the Black Sea shore, there is a limestone maze 240 metres long that has no natural opening to the surface. A geological survey shaft cut into it in June 1986. Nobody had been inside it before, and on the available evidence nothing from the surface had washed into it for a very long time either. Conditions vary sharply by depth, and the distin…