The Sassi of Matera are two districts of Matera, the Sasso Caveoso and the Sasso Barisano, formed by rock buildings built in the natural quarries of the Materan Murgia and inhabited since the Paleolithic. The Sassi constitute an entire city excavated in the calcarenitic rock, locally called "tufo", an articulated housing system, perched along the slopes of a deep valley with singular and surprising natural characteristics: the Gravina. Built, elegant and articulated structures alternate with underground labyrinths and cavernous meanders, creating a unique landscape of great effect.