The Sassi originate from a prehistoric troglodyte settlement and are suspected to be among the first human settlements in Italy. There is evidence that people were living here as early as the year 7000 BC.
The Sassi are houses dug into the calcarenitic rock itself, which is characteristic of Basilicata and Apulia, locally called "tufo" although it is not volcanic tuff or tufa. The streets in some parts of the Sassi often run on top of other houses. The ancient town grew up on one slope of the ravine created by a river that is now a small stream. The ravine is known locally as "la Gravina". In the 1950s, the government of Italy forcefully relocated most of the population of the Sassi to areas of the developing modern city.