The stone spheres (or stone balls) of Costa Rica are a collection of over three hundred petrospheres in Costa Rica. Some of them are quite small, a few inches in diameter, but some of them are as large as six feet in diameter weighing 14 tons. Most are sculpted from gabbro, the coarse-grained equivalent of basalt. There are a dozen or so made from shell-rich limestone, and another dozen made from a sandstone.
The stones are believed to have been carved between 200 BC and 1500 AD. However the only method available for dating the carved stones is stratigraphy, and most of the stones are no longer in their original locations. The culture of the people who made them disappeared after the Spanish conquest. The balls seem to be randomly placed and have no apparent purpose.
The spheres were discovered in the 1930s as the United Fruit Company was clearing the jungle for banana plantations. Workmen pushed them aside with bulldozers and heavy equipment, damaging some spheres. Additionally, inspired by stories of hidden gold workmen began to drill holes into the spheres and blow them open with sticks of dynamite. Several of the spheres were destroyed before authorities intervened. Some of the dynamited spheres have been reassembled and are currently on display at the National Museum of Costa Rica in San José.
Numerous myths surround the stones, such as they came from Atlantis, or that they were made as such by nature. Some local legends state that the native inhabitants had access to a potion able to soften the rock.
It has been claimed that the spheres are perfect, or very near perfect in roundness, although some spheres are known to vary by 5 centimetres (2.0 in) in diameter until 257 centimetres (104 in). Also the stones have been damaged and eroded over the years, and so it is impossible to know exactly their original shape.