The Marble Cave of Gadime, twenty kilometres south of Pristina in Kosovo, was found in 1967 by a villager cutting stone in his garden who put his pick straight through into it. What he broke into is rare. Caves are normally dissolved out of limestone, but this one is cut into marble, which is dense and gives water almost nothing to work with. Water could only get in along the cracks, so nothing here wanders. The galleries run in long straight lines tracing the tectonic fractures that split the rock, and they turn where the fractures turn. Where those fractures meet the older schist lying beneath the marble, the water was forced sideways, and the widest halls opened along that seam.
The lit walk takes you through halls where the stone is still wet. Stalactites hang in dense clusters over your head above blunt, rounded stalagmites, and every surface shines because water is still reaching it; in other chambers the drip has slowed and the stone has gone dull. The colour is the surprise. Marble and its crusts run white and rust-orange through to blue and green, and that is the rock's own palette rather than the lamps. In one gallery needle-thin aragonite crystals burst out of the wall beside you in sprays up to thirty centimetres long, growing sideways and upward with no regard for which way is down. Only a handful of caves anywhere carry aragonite this large. In another, two formations lean toward each other with a few centimetres of air left between them; the guides call them Romeo and Juliet, and stone grows far too slowly for them to touch on any human timescale. The lit route you walk covers a fraction of the 1,260 metres surveyed here, and dark openings lead off it the whole way. About a thousand bats of eight species roost back there, and beneath them live crickets feeding on the insects in the guano. Nothing grows this far from daylight, so everything down here is ultimately eating what the bats bring home each night.