It is a millenary practice, a little in all world cultures, to make a sacrifice when one begins to build a building, especially if of importance . Something in the foundation wall symbolic, a venial or affective value, is a very common apotropaic rite, a ritual born from the will to seize the favor of the gods of the place and remained all today an auspicious ceremonial.
Often confined to symbols and objects, in some periods and cultures, this superstition takes on extreme connotations and there are hundreds of them documented cases of men, women and children, walled alive, many of them also in Europe.