The entrance leads into a corridor, on whose sides are often open niches, that leads to the round chamber. A spiral stone stair, leading to upper floors (if present) and/or to a terrace, was built within the thick walls and it was illuminated by embrasures. The Nuragic towers might have as much as three corbel chambers one on top of the other. In complex Nuraghes corridors were often present, sometimes corbelled, such as at Santu Antine, in which the corbelled arch corridors were superimposed on two levels, and reached a length of 27 meters.