Considerable speculation has been indulged in concerning the purpose of the _nuraghi_. For many years they were regarded as tombs, a view which was first combated by Nissardi at the International Congress in Rome in 1903. Further exploration since that time has placed it beyond all doubt that the _nuraghi_ were fortified dwellings. The form of the building itself is almost conclusive. The lowness of the door would at once put an enemy at a disadvantage in attempting to enter; it is significant that in the _nuraghe_ of Su Cadalanu, where the doorway was over 6 feet in height, its breadth was so much reduced that it was necessary to enter sideways. Arrangements were made for the closing of the entrance from inside by a heavy slab of stone, often fitted into grooves. The niche on the right of the passage clearly served to hold a man, who would command the passage itself and the staircase to the upper floor; he would, moreover, be able to attack the undefended flank of an enemy entering with his shield on his left arm. To the same effort at impregnability we may safely ascribe the fact that the staircase leading to the upper room did not begin on the floor-level of the passage, but was reached through a hole high up in the wall. Many of the _nuraghi_ are surrounded by elaborate fortifications consisting of walls, towers, and bastions, sometimes built at the same time as the dwelling itself, sometimes added later. Those of Aiga, Losa, and s'Aspru are among the most famous of this type. All the _nuraghi_ stand in commanding situations overlooking large tracts of country, and the more important a position is from the strategical point of view the stronger will be the _nuraghe_ which defends it. All are situated close to streams and springs of good water, and some, as for instance that of Abbameiga, are actually built over a natural spring. At Nossiu is a building which can only be described as a fortress. It consists of a rhomboidal enclosure with _nuraghe_-like towers at its corners and four narrow gateways in its walls. It is surrounded by the ruins of a village of stone huts. There cannot be the least doubt that in time of danger the inhabitants drove their cattle into the fortified enclosure, entered it themselves, and then closed the gates. Each _nuraghe_ formed the centre of a group of stone huts. Mackenzie has described such a village at Serucci, where the circular plan of the huts was still visible. The walls in one case stood high enough to show, from the corbelling of their upper courses, that the huts were roofed in the same fashion as the _nuraghi_ themselves. Another village, that which surrounds the _nuraghe_ of Su Chiai, was protected by a wall of huge stones.