Aliens, Lost Technology, Atlantis and 26 Tonnes of Stone: The Mystery of Costa Rica’s Spheres

“Absence of evidence is not evidence of absence.” - Martin Rees

During the 1930s, workers clearing tropical forest in southern Costa Rica for banana plantations began encountering something extremely unusual. Emerging from beneath the vegetation were enormous balls of stone. Some were relatively small, while others measured more than two metres across and weighed many tonnes. Most remarkable was their shape. Many were astonishingly spherical, despite having supposedly been created centuries before powered machinery, modern measuring equipment or precision engineering existed in Central America. The workers had accidentally uncovered what are now known as the stone spheres of the Diquís, and almost ninety years later we still cannot answer every question surrounding them.

More than 400 stone spheres have now been recorded in Costa Rica. This includes examples remaining at archaeological sites, spheres recovered from private ownership and others involved in official recovery processes. How many originally existed is impossible to determine. Many were moved before archaeologists properly recorded them, others were damaged, some disappeared into private gardens and several were deliberately blown apart because treasure hunters believed gold was hidden inside them. The number manufactured by the original civilisation could therefore have been considerably higher than the number surviving today.

The largest known example is located at El Silencio. It measures approximately 2.66 metres across and weighs somewhere around 24 to 26 tonnes depending upon the estimate used. It is made from granodiorite, an extremely hard igneous rock. Looking at something of this size immediately raises an obvious question. How does a society without modern cranes or powered cutting machinery take a block weighing roughly the same as several elephants, transport it from its stone source and transform it into an extraordinarily regular sphere?

Archaeologists have an explanation, although parts of it remain theoretical. The generally accepted view is that the spheres were created by the pre-Columbian societies of southern Costa Rica, particularly those inhabiting the Diquís region. Archaeological sites containing spheres also contain houses, artificial mounds, paved areas, pottery, sculptures, gold objects and stone tools belonging to these societies. Some spheres remain positioned beside important buildings and ceremonial spaces, strongly linking them with the communities that occupied the area.

The proposed manufacturing method involved repeatedly hammering and pecking large blocks of stone, possibly using heat to fracture layers, before grinding the surface with abrasives such as sand. Wooden measuring devices may have been used to check the curvature as work progressed, and some spheres appear to have been polished. This is certainly possible, and there is archaeological evidence of stone-working tools within these communities. What is less certain is exactly how the entire process worked in practice, especially when applied to the largest examples.

This is where the story becomes much more interesting than simply saying that somebody hit a rock with another rock until it became round. Knowing that ancient people possessed stone tools does not automatically explain every stage involved in creating a 24-tonne sphere. How were extremely accurate curves repeatedly measured across such a large surface? How many years did individual spheres take to produce? How was the rock rotated while being worked? How were enormous unfinished or finished stones transported across uneven tropical terrain? What wooden frameworks, levers, abrasives, templates or other devices might have existed but subsequently decomposed? On several of these questions, archaeology simply does not have complete answers.

Even the official UNESCO material describing the Diquís sites acknowledges that the precise methods and tools used in production remain under investigation. That is important because there is a difference between saying that ancient stone-working techniques provide a plausible explanation and saying that the entire manufacturing process has been conclusively reconstructed. It has not.

This opens the door to another possibility: lost technology.

The phrase immediately produces images of lasers, electricity and mysterious machines, but lost technology does not necessarily mean anything that dramatic. Human beings have repeatedly lost specialist techniques throughout history. Methods known to one group of craftsmen can disappear when those craftsmen die, societies collapse or technologies are replaced. Wood, rope, leather and other organic materials rarely survive for centuries in tropical conditions. It is therefore entirely reasonable to wonder whether the people producing the Costa Rican spheres possessed sophisticated measuring systems, specialist tools, mechanical aids or manufacturing techniques that have simply vanished from the archaeological record.

Some people take this possibility considerably further. They argue that the spheres may represent the surviving remains of a forgotten technologically sophisticated civilisation that existed before the societies normally credited with their construction. In this interpretation, later inhabitants may have inherited, moved or reused objects created by an earlier culture. The extraordinary regularity of some spheres and the difficulty involved in producing the largest examples are presented as evidence that ancient engineering may have been considerably more advanced than conventional archaeological reconstruction allows.

There is currently no direct archaeological evidence proving the existence of such an earlier technological civilisation in the Diquís region. No unknown machinery, advanced metal-cutting equipment or separate industrial layer has been discovered beneath the recognised pre-Columbian settlements. However, the idea survives because the objects themselves are so unusual and because so much information about their original locations was destroyed before systematic archaeology began.

Unfortunately, modern people contributed enormously to that mystery.

When the United Fruit Company developed plantations in the region during the 1930s and 1940s, spheres were frequently moved because they were in the way. Others became fashionable ornaments and were transported to homes, public buildings and gardens. Moving an archaeological object is particularly destructive when its position may have formed part of its meaning. Once a sphere has been dragged miles from where its creators placed it, any alignment with another sphere, building, mountain, sunrise or star has been permanently lost.

Some suffered an even worse fate. Rumours spread that the spheres contained gold, prompting people to drill or dynamite them. Unsurprisingly, the inside of a giant stone sphere turned out to contain considerably more stone. Several were shattered before authorities began protecting them. Archaeologists have painstakingly reconstructed some damaged examples, but it is impossible to reconstruct the information destroyed with their original settings.

That lost context helped create another collection of theories. Some researchers and writers suggested that arrangements of spheres formed astronomical alignments. Others proposed that they represented maps or navigation systems. Claims appeared that lines drawn between particular spheres pointed towards distant sites elsewhere in the Americas or across the Pacific. Atlantis inevitably entered the discussion, with suggestions that the spheres were remnants of an advanced civilisation destroyed in some forgotten catastrophe.

Then came the extraterrestrials.

The ancient alien theory follows a familiar pattern. An ancient civilisation produces something that seems extraordinarily difficult using the technology traditionally attributed to it, so the possibility is raised that knowledge arrived from somewhere else. The remarkable shape of the Costa Rican spheres made them obvious candidates. Some writers proposed that extraterrestrial visitors either manufactured the spheres themselves or provided ancient inhabitants with the technology required to make them.

The theories became stranger still. The spheres have been described as navigational markers for spacecraft, devices capable of storing energy, components in a worldwide ancient energy network and even markers associated with portals or dimensional gateways. Costa Rica's official Diquís heritage authorities acknowledge that theories involving extraterrestrials, Atlantis, navigation devices, esoteric energy and doors between dimensions have all been attached to the spheres.

There is no physical evidence proving any of these claims. No extraterrestrial material has been recovered from a sphere and nothing resembling alien machinery has been found beside one. Nevertheless, the alien theory remains popular because the spheres are visually almost perfect objects for such speculation. A twenty-tonne stone ball sitting mysteriously in a tropical landscape simply looks as though it ought to have an unusual explanation.

One important claim also needs qualification. The spheres are frequently described online as mathematically perfect, sometimes with suggestions that their dimensions vary by only millimetres. Archaeologists who have actually measured them do not support that extreme interpretation. They are remarkably spherical, particularly considering their size and age, but they contain imperfections, damage and weathering. Some early claims of near-impossible precision were based upon measurement techniques incapable of producing the accuracy later attributed to them.

This does not make them unimpressive. Quite the opposite. Removing the claim of mathematical perfection still leaves ancient craftsmen producing enormous, highly regular stone spheres from extremely hard material and moving some of them substantial distances. Explaining them does not become easy simply because they are not perfect to the tolerances of a modern engineering workshop.

Their purpose remains another mystery. Archaeological context suggests that large spheres were associated with powerful individuals, important residences and ceremonial areas. At Finca 6, spheres were positioned around significant structures and at important entrances. They may therefore have demonstrated authority, rank and prestige. If a chief could command enough people and resources to create and transport a twenty-tonne polished stone sphere, placing it outside his residence would have sent a reasonably clear message regarding who was in charge.

Other spheres were positioned in arrangements that may have possessed astronomical or ritual significance. Some formed straight, curved or triangular alignments. Whether these corresponded with particular stars, solar events or agricultural calendars remains uncertain because so many were moved before their original positions could be accurately recorded. We are therefore left with fragments of a system whose creators never wrote down what it meant.

Perhaps that is the greatest mystery of the Costa Rican spheres. We possess the finished products but not the knowledge that produced them. Archaeologists can reasonably connect them with the Diquís societies, identify likely stone sources and demonstrate that those societies possessed sophisticated stone-working traditions. What we cannot do is travel back and watch a 24-tonne sphere being created from beginning to end.

It is therefore reasonable to leave room for lost knowledge. Perhaps the accepted combination of stone tools, abrasives, heat and enormous amounts of labour really does explain everything. Perhaps the craftsmen also possessed measuring systems, mechanical methods and specialist techniques that have completely disappeared. A much more speculative possibility is that they inherited knowledge from an earlier civilisation whose technological abilities we have underestimated.

The evidence currently favours the known pre-Columbian societies of Costa Rica rather than Atlantis or extraterrestrial visitors, but evidence and certainty are not the same thing. History has repeatedly shown that ancient people were capable of engineering achievements later generations underestimated, and the absence of surviving machinery does not necessarily mean that every technique they possessed has survived for us to examine.

More than 400 stone spheres remain as evidence that somebody in ancient Costa Rica knew exactly what they were doing. Some weigh only kilograms. Others weigh more than twenty tonnes. Many were transported away from the stone from which they were made and placed according to patterns whose meanings have largely disappeared.

We know where many of them were placed and we know which ancient societies lived around them.

We have theories about how they were made. What we do not have is the craftsman standing beside one explaining how he did it. Until we do, there will always be enough space between those two things for lost technology, Atlantis and perhaps even the occasional alien.