The cave covers an area of 4.5 km² and was declared a provincial reserve (Reserva Provincial Caverna de las Brujas) in 1990. It is a solutional limestone cave, formed by Jurassic sedimentary rock that rose from the ocean as the Andes emerged during the Tertiary. The rock was eroded by underground water currents and vertically fractured. Further erosion occurred at the end of the last Ice Age, when precipitation was much heavier than today.
The Witches' Cave is home to many peculiar speleothems (such as stalactites and stalagmites), deep underground water galleries, and large vaulted spaces called Sala de la Virgen (Virgin Room) and Las Flores (The Flowers). It hosts a particular fauna adapted to live without solar radiation (spiders and springtails). The galleries closest to the entrance are occasional shelters for bats and mice.
About 6 km of the cave's passages have been explored. The site is one of the major tourist attractions in southern Mendoza, but visitors are only granted access (with a guide and proper equipment) to the first 200 m of galleries, which are already damaged by careless human visitors.