Reutlingen, nicknamed "The Gate to the Swabian Alb" , is a district (Kreis) in the middle of Baden-Württemberg, Germany. The former free imperial city (until 1802) reached the limit of 100,000 residents in 1989. It is the ninth-largest city in Baden-Württemberg. Reutlingen district's neighboring districts are (from north clockwise) Esslingen, Göppingen, Alb-Donau, Ostalbkreis, Biberach, Sigmaringen, Zollernalbkreis and Tübingen.