Grain pits are silos dug in the ground; they were used to store wheat. Such pits were often pear-shaped, with small openings and diameters of up to three metres at the widest point. To preserve the grain in an anaerobic environment, the pits were filled to the top and then hermetically sealed. The oxygen remaining in the silo would alter the grain in contact with the earthen walls, but would be quickly used up as it turned to carbon dioxide. Wheat could thus be kept for several years without fermenting and without being attacked by insects.
Among these silos, certain cylindrical pits may be distinguished by their greater depth and by the existence of internal compartments associated with a raised floor. This arrangement solved the problem of humidity by creating an opening for coals or heated stones to be introduced, thus drying out the silo's contents. We know that a part of the stored grain was thus steamed or grilled.
These pits, which were normally grouped together a short distance from dwellings, were no doubt used to store excess grain from the harvest. After a period of use-which we believe to be relatively short-these silos were often converted into waste pits.