Rock formations of Arches, Bryce Canyon, Al Naslaa, and Madain Saleh. And whatnot.
Stalactites, Stalagmites, and Whatnot.
Cave denizens, of Interest.
Stalactites are formed from water running through what is generally limestone. The accompanying Stalagmites are then brought into being from the calcite which drips from said stalactite. Seems to work out pretty well.