The moon landing was closer to Cleopatra than the pyramids being built. Even to us now the pyramids are incredible and some of it is still a mystery, but what about the people of Egypt a thousand or more years after its construction, what did they and perhaps even outsiders know about them?
I found this old thread that might be able to help you: http://www.reddit.com/r/AskHistorians/comments/1msowj/did_roman_or_egyptian_historians_in_100_bce_know/
Actually the last pyramids were stopped around the new kingdom - which is around 1800 BC, which is just slightly closer than the moon landings.
However, around 1300, some of the pyramids were being refurbished, and I think around 500 or 450 BC (memory isnt perfect but you get the idea) Herodotus visited the pyramids and wrote how they were built in detail. So, it wasn't exactly a mystery to them, and even today, the building of the pyramids aren't very mysterious (you can even see some pyramids where they were learning the technique)
So for cleopatra, it wouldve been as simple as walking down to the library at alexandria and asking the scribe for the scroll.