In rural China, in a location that is considered to be uninhabitable to humans, there are three openings in Mount Baigong that contain hundreds of rustic iron pipes. Some of the pipes run deep into the mountain, others run to a nearby lake. There are more pipes in the lake bottom and there are pipes scattered along the shoreline. The pipes are cleanly cut and not jagged, so they appear to have had a use at one time. This all seems mundane: some pipes sticking out of the ground in China, but archeologists dated the pipes to a time when humanity was just getting familiar with fire, making casting iron impossible.
No, do these tell a story about Aliens, or pre dated Humans....Nobody knows.