Nuraghe Arrubiu, reached a height of 25–30 meters. The entrance leads into a corridor, on whose sides are often open niches, that lead 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. Today fewer than 7,000 nuraghes remain standing; their number was originally larger. Nuraghes are most prevalent in the northwest and south-central parts of the island. Function There is no consensus on the function of the nuraghes: they could have been rulers' residences, military strongholds, meeting halls, religious temples, ordinary dwellings or a combination of any of these things. Some of the nuraghes are, however, located in strategic places – such as hills – from which important passages could be easily controlled. They might have been something between a "status symbol" and a "passive defence" building, meant to be a deterrent for possible enemies. Nuraghes could also have been the "national" symbol of the Nuragic peoples. Small-scale models of nuraghe have often been excavated at religious sites (e.g. in the "maze" temple at the Su Romanzesu site near Bitti in central Sardinia). Nuraghes may have just connoted wealth or power, or they may have been an indication that a site had its owners. Recent unconfirmed theories tend to suggest that Sardinian towns were independent entities (such as the city-states, although in a geographical sense they were not cities) that formed federations and that the building of these monuments might have depended on agreed-on distributions of territory among federated unities. In 2002, Juan Belmonte and Mauro Zedda measured the entrance orientations (declinations and azimuths) of 272 simple nuraghes and of the central towers of 180 complex ones. The data revealed clear peaks corresponding to orientations pointing to the sunrise at winter solstice and to the Moon at its southernmost rising position. These alignments remained constant throughout the history of nuraghe. The most common declinations revealed were of around −43° for the earlier nuraghes, shifting to just −45½° for the later. Zedda has suggested that the target is likely a star,