How it began
The spheres were made in the Diquís Delta of southern Costa Rica by precolumbian chiefdom societies. UNESCO dates the settlements that contain them to 500 to 1500 CE. Wikipedia reports that the first spheres are believed to date from about 600 CE, with most made after 1000 and before the Spanish conquest. They are attributed to the Diquís culture, which no longer exists.
Before it existed
The settlements where the spheres stand also contain artificial mounds, paved areas and burial sites. UNESCO presents them as evidence of the complex social, economic and political systems of chiefdoms in the period. The spheres are thought to have been set in lines along the approach to the houses of chiefs, though their exact meaning remains uncertain.
How it works
The spheres range from 0.7 to 2.57 meters in diameter. According to Wikipedia they appear to have been made by hammering natural boulders with other rocks and then polishing the surface with sand. No metal tools were involved. UNESCO singles out the perfection of their shape, and their number, size and density, as what makes them distinctive.
What lasted
The spheres are the best-known stone sculptures of the Isthmo-Colombian area. Many were moved from their original positions during agricultural development in the 20th century, which UNESCO notes as damage to the sites, while those that stayed buried under sediment were protected. Archaeologists have proposed that they represent the sun, the moon or other celestial bodies.
Where it stands today
Four archaeological sites with spheres were added to the UNESCO World Heritage List in June 2014, and in July 2014 Costa Rica declared the spheres a national symbol, a step first proposed in 2011. The sites are protected under national heritage law and managed by the National Museum of Costa Rica, with excavations centered on the site called Finca 6.
