Man Made or Nature Made?

Humans are great constructors. They can build large houses, bridges, harbours etc. There are, however, some formations which humans have believed to be man made, which was not. By the shores of Greece, snorklers discovered what was first thought to be a harbour built by men, but lost to the sea. It was not. It turned out to be natural formations, formed about five million years ago. Humans are not the constructors of every seemingly artificial artifacts. I like humans anyway.