The property includes four archaeological sites located in the Diquís Delta in southern Costa Rica, which are considered unique examples of the complex social, economic and political systems of the period AD 500–1500. They contain artificial mounds, paved areas, burial sites and, most significantly, a collection of stone spheres, between 0.7 m and 2.57 m in diameter, whose meaning, use and production remain largely a mystery. The spheres are distinctive for their perfection, number, size and density, and placement in original locations. Their preservation from the looting that befell the vast majority of archaeological sites in Costa Rica has been attributed to the thick layers of sediment that kept them buried for centuries.

Źródło: World Heritage Convention
http://whc.unesco.org/en/list/1453