The balls made me think of this:
They are stone spheres in Costa Rica made by the indigenous people. At least 300 of them have been found ranging in size from a few centimetres to over two meters in diameter. Some weigh 16 tons. Almost all of them are made of granodiorite, a hard, igneous stone. They are nearly perfect spheres, very smooth. Scientists believe the stones were first created around 600 A.D., with most dating to after 1,000 A.D. but before the Spanish conquest. to pre Columbian times.
No one really knows why they were made. They were done by hammering, pecking, and grinding on the stones, with stone tools.
I thought they were beautiful, especially when you think of the hundreds of hours that must have gone into shaping the larger ones.
They have now become a common motif in Costa Rica and there are many modern reproductions.