instruction: Who built the great pyramid of Giza?
output: Mainstream archaeologists claim that the great pyramid was built by pharaoh Khufu. There is not much evidence to support that claim given that the Egyptians left no written accounts of the methods and timing of the pyramid construction.
  
  Some scientists have proposed the theory that the great pyramids were actually built by a lost civilization. This theory claims that a cataclysmic event whipped out this civilization at the end of the period known as the Younger Dryas.