http://thelittersitter.com/defau11.php 
Sinhyeon All 4 sides of the Great Pyramid are more precisely aligned with the cardinal points than any other building in the world today.
The incredible accuracy makes the Great Pyramid face true north by an error of only 0.05 degree! As a comparison, a more recent attempt at a building perfectly facing the north was the old Observatory of Paris, in 1667. It only reached error of 0.25 degree.
Why did they make sure the Pyramid was so precisely aligned? Did that have a specific meaning? Or was it simple pure demonstration of engineering abilities?
There is no doubt that their astronomical knowledge was beyond anything we can imagine. And as we often write it is only possible to reach such levels of accuracy when you can actually use tools that will measure this accuracy.
A question that is now too often asked about the Great Pyramid of Giza: how could they do what we can’t do today? “Sundials” like Egyptologists will say?
And what if we tell you that the pyramids of the Giza plateau are also perfectly aligned with the stars of Orion belt?