Actually, a metal machinist from the Midwest named Christopher Dunn has a fascinating theory that the great pyramids may have actually been 'power plants' of a sort.

Giant harmonic resonators that siphon energy off of the earths expansion and contraction caused by orbit of the moon.

http://www.amazon.com/Giza-Power-Plant-Technologies-Ancient/...

His writing is a bit dense, and maybe not as smooth as it could be...but his exploration of the possibility is quite impressive.