The stone spheres of Costa Rica, recognized to be some the of the strangest mysteries of the archeology, were discovered during the 1930s in the Diquis Delta of Costa Rica, also known as the Sierpe River, near the little towns of Palmar Sur and Palmar Norte. The spheres were found as far apart as by the mouth of the Coto Colorado River, on the Isla del Cano and near Golfito. In Costa Rica, some people now use them to decorate their gardens and thus they can be seen just about everywhere in the country. They vary considerably in size and can be as small as 2 centimeters up to over 2 meters across and can weigh up to 16 tons. Most of them were carved out of a very hard igneous stone called granodiorite. They are classed as monolithic sculptures made by human hands. There are over 300 of them spread out all over the country; however, new ones are always being discovered.