4The Baigong Pipes
In an area of China not known to ever contain people, let alone industry, there are three mysterious triangular openings on top of a mountain containing hundreds of ancient rusty iron pipes of unknown origin. Some of the pipes go deep into the mountain. Some of them go into a nearby salt water lake. There are more pipes in the lake, and more still running east-west along the lake shore. Some of the larger pipes are 40 cm in diameter, are of uniform size and are placed in what seems like purposeful patterns.
Hey, vagina caves.
So what's the big deal? Well, archaeologists have dated the pipes to a time when people were still trying to figure out how to cook meat without setting their back-hair on fire, let alone casting iron.
Why Can't They Solve It?
Oddly, the pipes are clean of debris despite being older than Zeus. This suggests that they were not simply shoved into the ground for the hell of it, but actually used for something. Oh, and did we mention the mountain is completely inhospitable to human life?
As usual, a faction of nutjobs believes the Baigong Pipes to be an ancient astronomy lab or even spacecraft launching site left by extraterrestrials. This is possible, since the pipes contain a proportion of silica close to what occurs on Mars. Of course, the manhole cover outside your house does also, so take that with a grain of salt.
Some say they are a hoax. We must politely remind those people that you can't wipe your ass in China without the government knowing, let alone set up a fucking iron forge and start burying pipes in the ground for the purpose of confusing passers-by.
Long ago, a group of frustrated fishermen with lots and lots of spare time spent their whole lives building a plumbing system to drain that nearby lake. Then they figured they'd just walk right down there with wheelbarrows, scoop up the fish and eat like kings.
3The Giant Stone Balls of Costa Rica
Costa Rica and a few surrounding areas are scattered with giant stone balls. They are smooth and perfectly spherical, or nearly so. Some of them are quite small, a few inches in diameter, but some of them are as large as eight feet in diameter weighing several tons.
They have been chiseled to perfection by persons unknown, despite the fact that Costa Rica is still not scheduled to enter the Bronze Age until 2013. The are balls everywhere and serve no apparent purpose, like a swing club on Gentlemen's Night.
And God said, "It's nice, but could use some more purposeless balls."
Some of the balls have been blasted apart by locals hoping to find gold, coffee beans, or even babies. Some have been rolled around, but some are too heavy to move even with a bulldozer. Not that they have bulldozers in Costa Rica.
Why Can't They Solve It?
About the most useful information anyone has gotten is that there are not, under any circumstance, any quarries anywhere near the balls. This information is actually useless considering the balls are carved from volcanic rock.
In 1,000 years the eggs of the stone men will hatch, and their offspring will emerge to rule the Earth.