What is the name of the oldest and largest of the three pyramids of Giza?

I read a book written by two experts I Egyptian history who said that no pharaohs were ever buried in the pyramids. The pyramids had some canals perforated to reach the central room, an, some time in the year the light of the sun, or moon, I cannot remember exactly, would reach this chamber. The three pyramids were specifically built, in relation to the Nile to resemble the alignment of the three stars in Orion’s Belt in relation to the Milky Way.