First, we have pyramids in both Egypt and in South America with the Mayan pyramids. So I'll assume you're referring to the Egyptian pyramids and not the Mayan pyramids. The Great Pyramid of Giza (also known as Cheops) is the oldest and stands as the largest and most intact of the three pyramids in the Giza pyramid complex. It is the oldest of the Seven Wonders of the Ancient World. The Great Pyramid of Giza, standing 455 feet tall. It was built for the pharaoh Khufu, and it is believed to have been constructed by the people of Egypt as a launching point for the soul of Khufu. This topic is something I've done a lot of research on so I can give more detail on this if you're interested, but I think this answers your question.

to troll the cosmos