Frozen Niagara and the Gypsum Flowers

Most of Mammoth Cave is not the dripping, glittering cave of postcards. Its endless corridors are mostly dry stone, because a hard sandstone caprock keeps water from seeping through the ceilings. But where that cap is worn thin, water breaks in and decorates the dark.

The most famous of these places is Frozen Niagara, a towering cascade of flowstone that looks exactly like a waterfall caught and turned to stone in mid-plunge. It is one of the best-known flowstone displays in the cave. Elsewhere, in the drier reaches along Cleaveland Avenue, the walls grow a very different kind of ornament.

There, mineral-rich water pushes crystals of gypsum out of cracks in the rock, blooming into delicate white petals and curling ribbons that look like frost flowers or twists of celery. One chamber is so covered in white gypsum balls that it is called the Snowball Room, as if snow had been flung against the ceiling and frozen there. Between the frozen falls and the stone flowers, the cave keeps its most beautiful surprises for the places where the water finally gets in.