They’re ghostly pale, completely blind, and possibly live to be 100 years old — a clutch of “Slovenian dragons” has hatched in a cave in the southwestern portion of the country.

They’re not really dragons, of course — they’re salamanders, and the super-rare species reproduces once every five to 10 years, according to a BBC report.

They are called “olms,” and a clutch of eggs started to appear back in January in Postojna cave, a popular tourist destination that has its own aquarium. It’s extremely rare to observe baby olms developing and hatching, making it a one-of-a-kind event for science.

The first of the 23 eggs hatched on May 30, and a second baby olm, hatched just a couple days later.

No one caught the first egg hatching, but an infrared camera was able to spot the second one. Hopefully, all 23 will hatch in the next few weeks.

A total of 64 eggs were laid by a female, but only 23 embryos actually developed. The remaining eggs decayed or were lost to fungal infections, which is normal.

The baby dragons have a low survival percentage in the wild, with only a couple of adults surviving out of 500 eggs, according to the report.

“Due to the increasing pollution of subterranean waters and the human impact on the underground ecosystem the number of living olm specimens has been on a steady decline and olms were in 2009 also listed as an endangered species by The World Conservation Union,” according to a Postojna Cave statement. “Sir David Attenborough, the legendary British naturalist and author of numerous BBC documentaries, picked olms as one of ten endangered animal species that he would take on his very own ‘Noah’s Ark.’

“On Saturday 30 January 2016, one of the Postojna Cave guides noticed that there was an olm egg attached to the glass wall of the aquarium in the Postojna Cave’s Concert Hall. Next to the egg, there was a pregnant female olm guarding the egg. People around the world enthusiastically welcomed the first egg and are now eagerly waiting for the olm babies to hatch.”