The Cheops Pyramid is the only one of the three pyramids of Giza that has air shafts built into it. The angles of the shafts also align with celestial bodies. It is a complete mystery how the Egyptians could have placed these shafts so precisely and why the alignment with the stars was so important to them.
Perhaps this had to do with guiding the deceased bodies in the right direction. Not all of these shafts lead outside – some have an end, while others were used for ventilation.