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  Three options to the fascinating world of MD Viajes
The Fantastic Balls in el Cerro Piedras Bola

By: Édgar Anaya Rodríguez

Photo: Edgar Anaya RodríguezOne can see the curved shapes of the half-buried rocks, of the rocks that are completely out in the open and those of which one can only see a small part from among the shadows of the tree branches.

The wives of the giants who made their homes in this mountain a long time ago were large, heavy -very heavy-, slow moving and they did not say much.  How big are these rocks? Nine meters? twenty? How, when and where did they live? Almost none of the remains of these enormous beings survived the course of time; only that which would appear to be the most trivial: their toys, or their “stone balls,” as round as any other ball, and enormous, just as they were.

That was how some of the inhabitants of the place imagined the origins of these amazing rocks. Only some of them believe this, because others affirm that the rocks were made by extraterrestrials on one of their many journeys to the area. There are also those who believe that they were created by the pre Hispanic Indians.


If spheres are enigmatic in and of themselves, how much more so is this collection of rocks, which, when standing alongside them, make a human being look like an ant playing among marbles.

The questions, who, when, how and why these spherical rocks were created strike one the minute you set your eyes on them. Where they were made is the simplest question to answer: they are located in cerro Piedras Bola, a part of the Sierra de Ameca, an important volcanically active area about two hours’ walk from the nearest town, Ahualulco de Mercado.

Among these rocks, the first one to become famous was the one at the entrance to one of the mines in the area, called Piedra Bola.  Over time, Piedras Bola –in the plural- was the name given to the tree-covered hill where dozens of these spherical rocks in varying sizes are located (this is the only place where these rocks can be found). They have an average diameter of between one and two meters, although some of them have a diameter of up to three meters.

American geologists determined their origins and age after they had visited cerro Piedras Bola in 1968. Their analysis, based on research done on other naturally spherical rocks –those in New Mexico, USA, have similar origins but the biggest are only some 60 cm in diameter- concluded that the rocks were formed about 40 million years ago during the Tertiary period, through the chance crystallization of volcanic ash (attributed by some to have come from the Tequila volcano, only about 30 km away). This still candescent material, with temperatures estimated to reach between 500º and 800 º C, spewed from the volcano and flooded canyons. When it settled and cooled, concentric layers of molten rock underwent a crystallization process around glass particles contained in the molten material. These processes stopped due to cooling during different eras, depending on their location in the ash deposit. The result was these “balls,” formed in layers of different sizes, similar to an onion.

Over time, wind and climactic conditions have uncovered many of the spherical rocks buried in un-crystallized ash under the surface of the earth.


There are many examples of spherical rocks used as adornments in the San Fernando Plaza, near the Hidalgo metro station, in Motolinía Street, and in the Centro Médico Siglo XXI in Mexico City and in other towns and cities. Long before this, these rocks were perhaps also sculpted into spheres for decorative purposes: Olmec spheres carved out of basalt – a type of rock that has never been found in naturally spherical form- were found in the south of the state of Veracruz; these amazing shapes have also been found in such places as Honduras, Belize, and Costa Rica.

The 1.5 cm-diameter spherical rocks, found in El Palmar in the southeast of Costa Rica are not perfect spheres. Some 70 of these rocks were found by archeologists in the 1930s when a fruit company decided to sow orchards of fruit trees on these old flooded plains. Some of them are about two meters tall – higher than the average adult- and weigh up to 16 tons. However, the archeologists have concluded that these “balls” were carved by pre Hispanic Indians. Many of them are still half-buried in El Palmar, but others have been taken by crane to San José, the capital of Costa Rica and used to decorate peoples’ gardens.

Neither did the “balls” found in Jalisco, Mexico, escape the devastation caused by man when he comes across natural treasures.  In spite of the fact that they are not very well known, even in the region, several of them have been defaced by visitors, and there are only remains of many others that were blown up with dynamite when the rumor spread that they contained a gold center. The locals speak of a “mother stone” that was rolled down a hill and destroyed. This rock weighed 30 tons.

On the part of the hill called Las Torrecillas, soil erosion over the years left the “balls” perched on top of columns of earth, forming strange, formidable sculptures that daily are subject to being knocked down by ignorant idiots.  Instead of providing security for these historical formations and educating the public about them, there is only garbage and ignorance.

The spherical rocks at Piedras Bola -a masterpiece of nature- are yet another example of the marvels generally unknown in Mexico.


México desconocido No. 23 (1978) contains a description of what was in those days called “the giants’ ball.” “They look like they are ready to be used as bowling balls…the surface of the rock is rough and eroded by the weather and possibly by movements of the earth.”

The same article mentions that there is a unique adornment on the church in the town of Ahualulco de Mercado, the nearest town to cerro Piedras Bola. Today, that adornment sits on a pedestal in the gardens of the town’s main park. It is a spherical rock about 40 cm in diameter that served as a valve in the sluice gates of a nearby dam.  Some say that the rock is natural in origin, but that it was polished by someone; others say that it was sculpted. What is certain is that today it is a monument in honor of the rocks on the nearby hill and has almost become the symbol of the town of Ahualulco.

Photo: Edgar Anaya RodríguezAnother spherical rock almost one meter high lies in a space in front of a government office building, giving the welcome, as it were, on behalf of all the other similar rocks that have made Ahualulco famous.

Other carved rocks catch one’s attention in the town’s main park where you can also enjoy a regional corn drink called tejuino; these were made to flatten and extract the juice of the tequila-producing agave plant. Now retired from service, these round millstones are used solely for decorative purposes.

Trade in Ahualulco takes place in the tranquility of the plaza, between the palm trees surrounding the old buildings and the church with its Gothic-like tower. The atmosphere created by the mines in the nearby hills is no longer there. The mines that reached their peak about one hundred years ago were mainly lead and tin mines, and today they have been closed.


Leave Guadalajara on Highway No. 15 at Km 28 and take the turn-off for Federal Highway No. 70 to El Refugio. From there, take State Highway No. 17 to Ahualulco de Mercado. From there, take the special mountain path (you will need a guide) and you will find the cerro Piedras Bola some 10 km from the town.

Source: México desconocido # 305 / July 2002

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