The _Naus_ is a building with a supposed resemblance to a ship, one end being pointed and the other square. There are only a few on the island. Cartailhac mentions nine. Their length is from twenty-five to forty feet, height fifteen to eighteen. The finest, called ‘Nau d’Es Tudons,’ is near Ciudadela. It consists of large blocks of stone dressed with a hammer. The entrance is three feet square, leading to a sort of vestibule, whence another door opens into the main chamber, which is supported by pillars down the middle. These edifices are carefully built, and were evidently the tombs of great men. The _Taulas_ are two massive stones joined by a deep tenon and mortise and cut with remarkable care. The lower one is upright, and bears the upper one horizontally, like a table. They are in the centre of a building in the form of a semicircle forty feet across, the two ends being joined by a wall. Some twelve or fourteen _taulas_ remain. They must almost certainly have been altars, or the main features of temples. These _taulas_ appear to be closely allied to such edifices as Stonehenge or those at Avebury. In that case, they may be considered to date from about the same period, a date which has been ascertained astronomically by Sir Norman Lockyer--2000 B.C. The race of men who built them extended over Europe. They had dolichocephalic heads of average capacity, oval faces, aquiline noses, low foreheads, exactly like the skulls from the Basque provinces. They were not only spread over Europe, but established themselves in Mauritania (Morocco) and were probably the ancestors alike of the Guanches of Tenerife and the Baleares of these islands. The fourth class of prehistoric edifices consists of the _Talayuts_, so called from the Arabic ‘Atalaya’ or scout, hence watch-tower. Their height is usually not more than twenty feet. The largest, called ‘Torre Llafuda,’ is forty feet high. They are often forty feet in diameter at the base and six or seven feet less at the top. In 1818 Ramis gave a list of 195 of them, of which 142 were in fair condition. Since that time many have been used for limekilns or as quarries in building houses. They are all built of the rough vesicular limestone of the surrounding land, and the stones are generally roughly dressed and laid in courses. The walls are of enormous thickness, with a circular chamber in the centre, supported by a pillar of massive stones. There is usually a doorway on the south side.