Pyramids were built during the Old and Middle Kingdom. They are tombs to the Pharaohs and are the only standing ones of the ancient wonders of the world.
Perhaps it’s the question ‘how did they build them’ which makes them true wonders. Without, apparently any tools and instrumentation of the present times, such huge stone structures with mathematically correct measurements are positioned perfectly to give that unbelievable look.
Questions like the origins of the stones, where they were found, how they were cut to shape, moved to the desired location and mounted systematically on top of another etc are still not answered.
We have archeologists, historians and the like, analysing and giving us answers to things millions of years old. But not much on pyramids!
The best answer then would be what someone told me. ‘They’re built by beings of another planet or by gods!