Southeast of the Prison, we find the Cluster of Mortars, that some authors name the "Industrial Sector". The architectural features of its walls indicate it was considered important for the city. Bingham called it the "Ingeniosity Cluster". This was, seemingly, a very special place, since it had a double wooden door, with an inner locking system consisting of carved stone mortises and stone rods.

The two-meter high walls were built of well-carved stone, although the higher walls were of rougher stones. This difference indicates that perhaps the construction took place in tow stages. In this group, there is a room with two round mortars in it. Both of these are of the same diameter and type of carving. Some historians say that they were used for milling different products, or for weaving or making pottery as an "industrial" activity. However, the mortars do not seem to have been much used. Others indicate that they were the supports for aryballus (small, pointed amphorae) that contained chicha (corn beer). It has also been suggested that the "mortars" were filled with water to act as mirrors for observation of the stars on clear nights.

Modern astronomers, however, say no one can seriously make this claim, since it is far more practical to observe the sky directly, without the use of mirrors. Again, we know so little about the Incas, despite a generalized perception that they were intellectually advanced, that possibly an explanation rejected by modern science could have meanings which are hidden from us.