I have heard that to this day the Pyramids are so tightly fitted you can't fit a piece of paper between the blocks. However, this only seems possible if it hasn't settled unevenly in the past few thousand years, and that just seems so unlikely to me on such a large 'unsecured' building. From what I have heard the Pyramids are basically just a pile of really well cut stones. They aren't cemented together at all.
Did the Egyptians have advance knowledge of construction, or were they just lucky in where they were placed and materials used? Could this be duplicated today and last as long as the Pyramids have?
This feels a bit more like an engineering question, but I'll take a crack at it.
Everything I've seen and read on the subject says that the Great Pyramid of Giza (Of which I assume you are referring to), were build on very stable bedrock, so there wouldn't be much settling to be done. If you look at the pyramid Meidum, and it's advanced state of destruction. One of the hypothesized reasons for that is it was built on unstable bedrock, which could have lead to it's destruction.
EDIT: Read /u/Bunksy 's comment below for a better answer.
What do you mean by unsecured building? What is a secured building.