
These buildings were constructed using roughly worked limestone boulders collected from neighbouring fields and, later, the large water-collecting basins in the area. They were built directly on the underlying natural rock, using exclusively the drystone technique. The walls that form the rectangular rooms are double, with rubble cores, and are pierced by small windows. Fireplaces, ovens and alcoves are recessed into the thickness of the walls. The roofs, which are also double-skinned, spring directly from the walls, simple squinches allowing the transition from the rectangular to the circular or oval sections of the roofs themselves. These are built up of successive courses of grey limestone slabs, known as chianche or chiancarelle . The roofs of the larger building terminate in a decorative pinnacle, often apotropaic in function. There are ingenious provisions for collecting rainwater using projecting eaves at the base of the roof which divert the water through a channelled slab into the cistern beneath the house. Flights of narrow stone steps give access to the roofs.
The interiors are equipped with wooden fittings, such as door frames, barrel-vaulted niches, etc., and in some of the larger trulli there is a second storey formed from a wooden floor and reached by means of a wooden staircase. Stone fireplaces and ovens are ventilated through stone slabs covering them. The roofs are not painted and develop a patina of mosses and lichens; they sometimes bear mythological or religious symbols in white ash. By contrast, the walls of the trulli must be whitewashed at regular intervals, which has the effect of rounding the outlines of the stones, giving a brilliant homogeneous surface. The Monti quarter, which covers 6 ha on a hillside, contains 1,030 trulli . Its streets run downhill and converge at the base of the hill. The Aja Piccola quarter, with 590 trulli , is less homogeneous than Monti. The streets converge on a common farmyard where in feudal times the peasants were forced to thresh wheat.