Read this: The medieval city is a foundation of the Zähringer ruling family, which rose to power in Upper Burgundy in the 12th century. According to 14th century historiography (Cronica de Berno, 1309), Bern was founded in 1191 by Berthold V, Duke of Zähringen.

What year was Bern founded?
What is the answer? (If it cannot be answered, return "unanswerable")
1191