The Kheops pyramid is the oldest and the biggest one in Gizah. The accepted theory is that pyramids were built to be the tomb of the pharaohs, but the actual purpose of these pyramids is still not clear.
This one is almost 150 meters high. More than two and a half million stone blocks were necessary to complete it. Inside this huge monument pharaoh Kheops rested in peace.
Although there's actually not much to see, it is possible to get inside the pyramids, and see the rooms were the pharaohs were buried, and the rooms were all their treasuries were locked. If you suffer from claustrophobia you'd better not get in.