To this day we still don’t fully understand how the pyramids were built with the technology supposedly available at the time. Ancient Egyptian engineering and astronomy were so advanced and precise, some believe humanity itself was not capable of its feats, and surely alien technology must have been at work.
We are the aliens.
From the beginning humans have harnessed the power of the stars to guide them in monolithic feats of construction. Pharaohs believed when they died, they would become the stars in the sky, and return once again to the great beyond.