Costa Rica's Giant Stone Spheres

[YellowDragon]

I've only just recently heard about these. Since about the 1940's or so, people have been finding these strange stones in the Diquis Delta of Costa Rica and no one can explain them. They are perfectly round and range in size. Some weight as much as 16 tons which is insane. They are made of something called granodiorite. They were clearly made by humans (or something else) using some sort of technology but no one knows how the heavier ones got there.

Have you heard about this or looked into it at all?

[britanica]

I only heard of these in passing when reading or watching something else. I never really looked into them much further.

So is the mystery how they came to be and why they are there, or how they just ended up there to begin with? I would imagine finding them in strange areas would make anyone question things since those large ones had to be impossible to transport back then.