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.
Since then the cave has remained sealed by the Romanian authorities. Fewer than 100 people have been allowed inside Movile, a number comparable to those who have been to the Moon.
This is partly because the journey into the cave is extremely hazardous.
To enter, you must first lower yourself by rope 20m down a narrow shaft dug into the ground. The only light is from your helmet, which bounces around the walls as you descend.
You must then climb down through narrow limestone tunnels coated in an ochre clay, in pitch darkness and temperatures of 25 °C. These paths eventually open out into a central cavern containing a lake.
