They had this stuff all over the world! If you go searching you can find many pictures and even video. There are even HD pictures that were from the 1800's lol look up Jon Levy on youtube, he has a ton of research on these amazing buildings ;) I have a theory about them but it may be too far out there for most people to consider.. I think it was all built during Jesus' 1000 year reign on earth and that ended in the 1800's so now satan is loose and we are awaiting the final "fight" destruction of satan.
Just my thought idk.... I don't know a lot about the bible but I've put together a few pieces that could be a possibility. I just don't see regular people building all of those things.