For decades, the origin of the more than 200 stone spheres found along the South Pacific coast of Costa Rica, in the vicinity of the Terraba River, was a complete enigma. This led to speculation from which a number of theories sprung, some even mentioning the intervention of space visitors. However, little by little national and foreign archaeologists have been unraveling most of their secrets.
Mysterious sphere
Following years of investigation and analysis of different theories, the Costa Rican archaeologist, Ifigenia Quintanilla, has published the book "Pre-Columbian spheres in Costa Rica" (in English and Spanish), which collects all the verified information about these sculptures, the process of their elaboration and transport, as well as, the motives that led their creators to make them.
What is known today about them
They were made by the ancestors of the Boruca people, who made the first spheres about 1600 years ago and continued their elaboration non-stop until the arrival of Spaniards. About 250 spheres have been inventoried, but it is estimated that as many still exist hidden in the forest or underground. Their size varies, ranging from 4 inches to 8,2 feet in diameter and can weigh almost 16 tons. The rock of these spheres is made up of granite, "andesita" and sedimentary rock.
Transport of these rocks was a collective effort based on human strength, even though it is believed that rivers may have been used to transport them, but no evidence has been found of any type of boats to backthis theory. These sculptures, which on average, are 95% spherical perfect, were made in stages. Once the rock was chosen, they started with controlled fractures until they attained a more or less round shape.
Mysterious sphere
Next they heated and cooled the rock repeatedly to soften it and be able to improve the shape by means of more precise carving. Later they polish the spheres manually until they reached the perfection, which characterize them. The entire process was done using stone tools and supported only by the use of fire and water. The spheres were done in shops and later transported to their final location. This is known because no tools or other evidence of their manufacturing have been found in the vicinity of where they were discovered.
The reasons why they were made still belong to the realm of hypothesis. One of the better accepted theories indicates that they were used as symbols of power among the different groups. Another theory says that they could have been used to represent the elements of the cosmos, which would explain the fascination for the spherical shapes. Other reasons have not been discarded. As a matter of fact, it is possible that the creation of these spheres encompassed multiple causes and that their role in their society might have reached in a larger or smaller degree, many of the religious, political and social aspects of these communities.
People and Society 
