Hundreds of these petrospheres are known in Costa Rica, varying from handheld-sized to over two meters (six feet) in diameter. Early archaeological work in the region by Doris Stone (1943), Samuel Lothrop (1963), and others was prompted by the development of the area for the United Fruit Company's banana plantations.
Precolumbian residents of the Diquís created large, stone-lined platforms where modern researchers not only noted concentrations of the stone spheres, but also found groupings of spheres where no mounds were visible. At one site in particular, recent research uncovered spheres on either side of the entrance to a ramp leading to one of the major structures. Costa Rican researchers have also documented the spatial distribution, production, and function of these monuments.
The stone spheres are most often constructed from igneous rocks common to the area. Precolumbian artisans often obtained the source stone quite far from their intended destination, implying the work of a large team of individuals. With no metal tools, craftspeople pecked and ground away the surface with stone implements to create the perfect spheres that have captured the imagination of Costa Ricans and the global public. The cultural and symbolic significance of the spheres is not well understood; clearly, these monumental sculptures were prestige objects that marked the landscape around the ancient Diquís communities for residents and visitors alike to behold with awe.
In 2012 the Metropolitan Museum acquired a stone sphere, 66 cm (26 in.) in diameter and weighing 385 kg (850 lbs.), a gift of the Austen-Stokes Ancient Americas Foundation. Possibly from this region of Costa Rica, the object is a superb example of the artistic skill and vision of the Precolumbian sculptors who created it. A close examination at the time of donation determined that the sphere was made of andesitic rock.
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-----Resources and Additional Reading
Lothrop, Samuel K. "Archaeology of the Diquís Delta, Costa Rica, Vol. 51." Cambridge: Papers of the Peabody Museum of Archaeology and Ethnology, Harvard University, 1963.
Quintanilla, Ifigenia. Esferas precolombinas de Costa Rica. San José, Costa Rica: Fundación Museos del Banco Central de Costa Rica, 2007.
Stone, Doris Z. "A Preliminary Investigation of the Flood Plain of the Rio Grande de Térraba, Costa Rica." American Antiquity, Vol. 9, No. 1 (July 1943): 74–88.