pattern. In an 1897 photograph of the rione Monti (the district of the Mounts), the trulli are far less densely packed than today, being surrounded by enclosed gardens. The urban trulli still extant in Alberobello date from the eighteenth, nineteenth and twentieth centuries. After having undergone a process of densification in the first decades of the twentieth century, the trulli settlements began to be deserted during the second half of the twentieth century. The rural trulli, on cheaper land, ceased to be built when the cost of labour began to rise in the twentieth century. The sheer expense of handling the hundreds of tons necessary for a single house became prohibitive. Distribution The style of construction is specific to the Itria Valley, in the Murge area of the Italian region of Apulia. Trulli may be found in and out of Alberobello, and in the areas around Locorotondo, Fasano, Ostuni, Cisternino, Martina Franca, and Ceglie Messapica. Geology The Murgia is a karst plateau. Winter rains drain through the soil into fissures in the strata of limestone bedrock and flow through underground watercourses into the Adriatic. There is no permanent surface water, and water for living purposes must be trapped in catchment basins and cisterns. The surface forms a landscape of rolling hills and ridges punctuated now and again with dolines and other forms of enclosed depressions characteristic of karsts. Architecture Grouping The trullo is essentially a rural building type. With its thick walls and its inability to form multi-storey structures, it is an inefficient use of ground space and consequently ill-suited for high density multi story settlement. Being constructed of small stones, however, it has a flexibility and adaptability of form making the design most helpful in tight urban situations. In the countryside, trullo domes were built singly or in groups of up to five, or sometimes, in large farmyard clusters of a dozen or two dozen, but never for the occupancy of more than a single rural family. Materials Depending on the area, the building material used could be either hard limestone or calcareous tufa. Masonry Traditionally trulli were built using dry stone masonry, i.e. without any mortar or cement. This style of construction also is prevalent in the surrounding countryside where most of the fields are separated by dry-stone walls. Walls In Alberobello, the structural walls of a trullo are laid directly on the bedrock, after removal of the