The Sassi have been defined as a cultural landscape, to quote the definition with which they were welcomed into the UNESCO World Heritage Site. The term "Sassi" refers to the two districts that make up, together with "Civita" and "Piano", the historic center of Matera. The declension in the plural, therefore, derives from this duplicity and not, as many believe, from the fact that a house or a room within these districts is called "stone". The Sassi are arranged around and on the bottom of two valley furrows, shaped by the passage of water, channeled into the so-called "grabiglioni" on the bottom of the same. The Sasso Barisano, located along the road that went out from the city towards Bari, oriented to the north-west, contains sculpted portals and friezes. The Sasso Caveoso, which looks south towards Montescaglioso, recalls the shape of the cavea of a theater, with the houses arranged in steps. The cliff of Civita, which houses the Romanesque Cathedral, divides the two valleys. At the foot of the Civita and at the upper edge of the Sassi lies the Piano, the post-medieval historic center, beyond which the post-displacement Matera extends. On the opposite side of the Gravina di Matera, there is the plateau of the Murgia, with rock churches scattered along the slopes of the ravines, falling within the institution of the Murgia Materana Park and protected by it. Natural caves, underground architecture, cisterns, huge entrenched enclosures, farms, churches and palaces, follow and coexist, dug and built in the tuff of the ravines. (Wikipedia)