A GREAT MYSTERY is the perfectly round and spherical stones in Costa Rica. These stones are laying on the ground all over the place, and no one seems to know much about them and who made them. They are thought to date back to a previous extinct civilization called the Diquis Culture who lived in the area in about 800 to 1400 AD. There is some controversy around this dating. It is known the stones existed at that time, but they may have been around a long time before that.