Not so! Now normally when somebody says that to me, my usual response is "ok--why not?" There are a number of reference texts that explain what the problems are. Most significant technical problem is that we cannot achieve the tolerances of the block fits with carved stone and can't achieve the hardness of the blocks from any other stone based material. There are other issues but there are a number of texts out there which deal with this kind of problem. The best one I have had in my personal library I loaned to an architect friend of mine (who is an expert in stone and poured composite structures) who has not given it back--done by some composite scientist in Europe, his hypothesis is that the blocks were poured in place although his bottom line is that we lack the technical capability to do it that way today either.