The Sassi of Matera, Italy were designated a UNESCO World Heritage site in 1993. They are a well-preserved example of troglodyte settlements, with dwellings carved into the rock formations that are perfectly adapted to the local ecosystem. The earliest settlements date back to the Paleolithic era, and subsequent occupations illustrate significant stages of human history. Matera's Crypt of the Original Sin church contains important 9th century frescoes by Benedictine monks.