In the 1930s, the United Fruit Company was clearing the jungle in Costa Rica to make room for banana plantations when they stumbled across stone spheres of varying sizes. The 300 petrospheres named the Diquis spheres were discovered on the small island of Isla del Cano and the Diquis delta.
While some were carelessly bulldozed out of the way, others were drilled or dynamited because the workers thought the stone spheres had hidden treasure in them.
According to reports, the balls were created by the Diquis, a now-extinct pre-Columbian indigenous people of Costa Rica: "Between AD 800 – 1500 during the Chiriquí Period, the settlements grew into large communities around the alluvial lands of the Térraba River and its main tributaries, constructing large structures using round-edged boulders, paved areas, burial sites, and circular or rectangular mounds with stone walls. The Diquís reached an apex of cultural development during this period, with Diquís artisans creating elaborate ceramic, bone, and gold objects, and sculpturing stone spheres in important zones within the settlements."
Later on, the mysterious sphere balls were examined by Doris Stone, the daughter of a United Fruit Company executive, and her findings were published in American Antiquity. This created enough of a buzz to attract experts interested in carrying out further investigations of the spheres. It is assumed that they may have been placed in public plazas, or along the approach to the dwellings of the ruling elite or chieftains.
In 2014 the stones were declared a UNESCO World Heritage site and efforts are underway. Per reports, efforts are underway to preserve the remaining stones and their cultural significance.