The inhabitants of the Movile Cave are like no others. The “otherworldly” conditions of this Romanian cave, just a few miles west from the Black Sea, have been sealed up for around 5.5 million years. Although the air is poisonous and unbearably humid, this cocktail of factors has created a goldmine for biologists.

Fewer than 100 people have ever delved into the cave, according to BBC Earth. It was only discovered by humans in 1986, when workers of the Socialist Republic of Romania were looking for new ground to build a nuclear power plant. Nowadays, it is blocked off by the authorities and only accessible with special permission, although the central caverns are naturally “guarded” by a series of vertical shafts and narrow limestone tunnels.

Once in the depths of the cave, the air contains half of the amount of oxygen than usual and is high in carbon dioxide and hydrogen sulfide. It is also pitch black and hasn’t seen sunlight for at least 5.5 million years.

But within this harsh environment, scientists have so far identified 48 species. Among the creatures are an array of spiders, water scorpions, pseudoscorpions, centipedes, leeches, and isopods – 33 of which are totally unique to this one cave.

Most of the creatures in the cave have no vision and lack pigment. After all, who needs sight or to be pretty in the pitch darkness? They’re also, on the whole, a spindly bunch, with extra-long limbs and antennae that help them navigate in the darkness.

According to iflscience