Millions more years passed, and the widening river eroded to a new level, deeper and deeper into the limestone. The surface of the land began to show signs of sinkholes, where rain water drained directly into the limestone below. The cavities formed beneath the surface in the saturated limestone joined into one continuous channel as the underground river moved sideways between the layers of rock. The water continued to seep and move through the rock, dissolving and enlarging the soon-to-be caverns.
Still thousands, maybe even millions, of years later, the eroding river dropped to a new, lower level. The water drained from the underground river, leaving the cave high and dry. While another system of caves was forming at a new water level below, dripping water entering the dry rooms and passages started depositing calcium carbonate and other minerals in the form of stalactites, stalagmites, and numerous other dripstone features. The speleothems grow as long as groundwater enters the cave.