Great Pyramid of Giza

I found some interesting facts about the pyramids here http://greatpyramidsgiza.com/pyramids-facts/ but I would like to read more.

Share some resources if you have.

Thanks!

Some interesting facts: pyramid at Giza is heaviest object on earth. At the time it was built, the Nile was just a few yards from the pyramid. How did the builders know the soil conditions would tolerate such a heavy object? Its also aligned with the 4 points of the compass, but the compass was not discovered, or should we say re-discovered, until the Middle Ages. Also, if the pyramid was a tomb, why build the lower chamber, deep under the pyramid?