What they are
The Diquis stone spheres are human-made stone balls found in the Diquis Delta and nearby areas of southern Costa Rica, especially around Palmar Sur. More than 300 have been recorded, though many have been moved and some destroyed, so the original number is unknown. They range from small spheres of a few centimetres to examples more than two metres across and weighing several tonnes. Most are made of gabbro, a hard igneous rock, while some are of limestone or sandstone.
The spheres are impressive, but they are often described as “perfect” or as having no known maker, and neither is accurate. They were made by Indigenous communities of the region, and the best-made examples are very close to spherical, though not mathematically so.
How they were made
Stone for the largest spheres seems to have come from boulders, possibly gathered from sources in the nearby hills or river areas, and then shaped in several stages. Experiments and tool finds suggest that workers first fractured or flaked a boulder into a rough ball, then pecked its surface with hammerstones, and finally ground and polished it with abrasives. Some stones may have been heated and cooled to remove flakes, though this idea is not firmly established. Metal tools were not used for this work.
The precision required a clear idea of the shape and a lot of time. Because no workshops with complete sequences have been widely documented, the process is reconstructed from the objects and a small number of sites.
Dating
Dating is difficult because the spheres themselves cannot be dated by radiocarbon dating, as stone has no organic material. Archaeologists have instead dated the contexts in which some were found, such as house floors, mounds and surrounding deposits, using charcoal and associated pottery. A pottery sequence, built on principles like those of pottery seriation, helps place sites in time. These results suggest that sphere-making was most active in the period from about 500 to 1500 CE, with the exact start and end still debated.
Discovery and loss of context
The spheres became widely known in the 1930s, when clearing land for banana plantations exposed many of them. Moving them with heavy equipment and tractors was common, and some were dragged to town plazas, gardens and private homes, or damaged. Others were reportedly blown apart in the search for gold treasure. Archaeological work began in the 1940s, notably by Samuel Lothrop of Harvard, but by then many had already been shifted. Few spheres remain where they were first placed, which makes it hard to know how they were arranged or what stood nearby.
This loss is the main reason the meaning is unclear. A sphere moved from its original spot loses the information about its neighbours, its alignment and the buildings around it.
What they may have meant
Archaeologists generally agree that the spheres were linked to the chiefdoms of the region, and that they were symbols of rank or status. Observations at places where they were found in place support a few ideas:
- They were placed in front of or near the houses of leaders, to display wealth and the ability to command labor.
- Some were arranged in lines, triangles or groups, and a few were positioned on mounds.
- They may have marked boundaries or ceremonial places.
- Some researchers have proposed that alignments pointed to astronomical events or to the cardinal directions. This has not been established and rests on small samples, particularly given that so many have been moved.
All of these are interpretations. No Indigenous written account survives that explains the spheres, and the people who made them left no writing. Present-day Indigenous communities in southern Costa Rica have their own relationships with the landscape, and it is respectful to treat their views as part of the discussion.
Myths and claims
Popular writing has linked the spheres to Atlantis, to lost advanced cultures and to visitors from space. These ideas are examples of ancient astronaut claims, and they have no support in the excavated evidence: the stone, the tools and the pottery context all point to local Indigenous societies. Claims that the spheres are perfectly round or that they are impossible to make with simple tools do not hold up when they are measured.
Comparison and protection
Elsewhere in the Americas, monumental stone sculpture served political and religious aims in different forms, from the Olmec colossal heads of the Gulf Coast to the Moai statues of Easter Island in the Pacific. The Costa Rican spheres are distinctive for their simple, abstract shape.
In 2014 UNESCO inscribed a group of sites, which together with their spheres are named the Precolumbian Chiefdom Settlements with Stone Spheres of the Diquis, on its World Heritage List. Several spheres can be visited in a museum setting and at sites such as Finca 6. Many others remain in private hands or public places, and their care depends on continuing research and local interest.