Peña de Bernal is the world's third-largest monolith, and at 1,421 feet (433 meters), also one of the tallest. In the 1970s, the arrival of the new age proposed that the spring equinox was a good time to approach the rock to charge itself with cosmic energy. There have been a number of UFO sightings at Peña de Bernal, and some claim that UFOs would circle the rock at night or that Martians frequented the area. At the foot of the rock, there is a small business that claims to keep the skulls of those aliens.

It is called Gruta de Cuarzo (Quartz Grotto), although in reality it is the basement of a house decorated with millions of pebbles to form small murals of the myths of the place. In the rooms, you can see the eye of God, a UFO with neon lights on the wall, the myth of Quetzalcoatl the feathered serpent, and several gray "Martians" on the walls. If that is not peculiar enough, the last rooms exhibit a series of animal skulls (probably modified) as trophies as if they were strange creatures never seen before.

According to the myth, the skulls were taken by the oldest inhabitants of Bernal from the caves hidden in the rock. One of the most peculiar mysteries of the town is that its inhabitants are from the oldest communities in Mexico, a reason they attribute to the magical powers of the Bernal rock. It also has a collection of strange rocks that have also been found nearby and figurines that claim to be pre-Hispanic representations of aliens. 

Also offered with the tour is a sampling of the region's wines and a shop selling quartz advertising its magical healing properties.