Costa Rica does not have a large indigenous population or a real pre-Columbian presence. Some people say that the Spanish conquistadores killed all the natives they encountered, which would account for the relative dearth of indigenous art and artifacts in the country today. Others believe that Costa Rica never had a large indigenous population and that its land was mostly used as a travel route for native peoples moving from areas around Mexico to South America. However, Costa Rica does boast a set of very important—and unexplained—artifacts from pre-Columbian times. These are the stone spheres that archaeologists and land developers have unearthed in the country’s Diquís Delta region.

The spheres are of various sizes, and there are over 300 of them. The smallest are pebble-sized, and the largest weigh several tons. All are made from the same type of stone, identified by geologists as a sort of igneous rock. Despite their size, the spheres were all apparently formed by hand, although whose hand has not been fully determined. The spheres are not all perfect in shape, although some come very close to being perfectly smooth and round. Oddly, there have been no stones found in an unfinished state.

The spheres first appeared in the 1940s, when employees of the United Fruit Company excavated land near the Pacific coast. Scientists believe that the stones were shaped between 600 and 1500 AD, using various stone-shaping methods—rough shaping by means of temperature change and finer shaping through picking and grinding. After their discovery, the spheres soon became status symbols, and wealthy families paid to have the spheres transported to their homes from their original sites.

Fans of the occult and astrological theorists have long speculated about these spheres. Because many of the stones seem to have been found in geometric patterns and special alignments, some astrologers argue that the spheres are the work of extraterrestrials or evidence of some paranormal communication system. Some have even linked the spheres to the lost city of Atlantis. These theories are entertaining but wholly unsubstantiated by science.

Visitors to Costa Rica can see these stones everywhere. Several stand in front of the Legislative Assembly (Asamblea Legislativa) building. Other official buildings and schools also prominently display these spheres. And some are still in the front yards of private residences, nestled among ferns and flowers.

Click here for more about Costa Rica’s stone spheres.

Writing and editing by Beaumont Hardy Editing.