If the inclusion of Sicily in the megalithic area is doubtful there is fortunately no question about the island of Sardinia. Here we have one of the chief strongholds of the megalithic civilization, where the architecture displays its greatest variety and flexibility. The simplest manifestation of megalithic building, the dolmen, was up till lately thought to be absent from Sardinia, but the researches of the last few years have brought to light several examples, of which the best known are those of Birori, where the chamber is approximately circular in plan. The monuments, however, for which Sardinia is most famous are the _nuraghi._ A _nuraghe_ is a tower-like structure of truncated conical form, built of large stones laid in comparatively regular courses (Pl. II, Fig. 2). The stones are often artificially squared, and set with a clay mortar. The plan and arrangement of a simple _nuraghe_ are usually as follows (Fig. 17): The diameter of the building is generally under 30 feet. A door of barely comfortable height even for an average man and surmounted by a single lintel-block gives access to a narrow passage cut through the thickness of the wall. In this passage are, to the right, a small niche (_c_) just large enough to hold a man, and, on the left, a winding staircase in the wall (_d_) leading to an upper storey. The passage itself leads into the chamber (_a_), which is circular, often with two or three side-niches (_b b_), and roofed by corbelling, i.e. by making each of the upper courses of stones in its wall project inwards over the last. The upper chamber, which is rarely preserved, is similar in form to the lower. [Illustration: Plate II Fig. 1. MNAIDRA, DOORWAY OF ROOM H] [Illustration: Plate II Fig. 2. THE NURAGHE OF MADRONE IN SARDINIA To face p. 82] [Illustration: Fig. 17. Elevation, section and plan of a _nuraghe_. (Pinza, _Monumenti Antichi_.)]