sentences:  It is the most recently incorporated borough of Essen and also the largest in area, at 15.3 km².It belongs to the city district Stadtbezirk IX Werden/Kettwig/Bredeney and has 17,760 inhabitants as of June 2006.Kettwig's first mention was in a letter of Pope Innocent III to Heribert II of Werden dated May 19, 1199.