There are some astonishing similarities between the construction techniques of the ancient Egyptians and those of the native populations of South America.
These 2 civilizations never met each other. The only way both could've aquired this technology had to have been ancient aliens. It's not like 2 people on opposite sides of the world could get the same idea at the same time, especially when that idea is leaps ahead of any known technologies at the time. Ships aren't that fast, plus they hadn't even crossed the ocean with one yet, so it had to be spacecraft.

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