The Sassi di Matera are two districts of the Italian city of Matera, Basilicata, well-known for their ancient cave dwellings inhabited since the Paleolithic period.
The "Sassi" have been described by Fodor's as "one of the most unique landscapes in Europe". Along with the park of the Rupestrian Churches, it was named a World Heritage Site by UNESCO in 1993.
Wikipedia https://en.wikipedia.org/wiki/Sassi_di_Matera
UNESCO website http://whc.unesco.org/en/list/670
Address 55 Via Muro, Matera 75100, Italy
Coordinates 40°39'57.802" N 16°36'41.619" E