The Rötteln Castle (German: Burg Rötteln), located above the Lörrach suburb of Haagen in Germany, lies in the southwest corner of the German state of Baden-Württemberg, just 10 kilometres north-east of the Swiss City of Basel. The fortification was one of the most powerful in the southwest, and today, it is the third largest castle ruin in Baden. The castle has existed since the beginning of the 11th century. The first documented mention of a lord of Rötteln, Dietrich von Rötteln, the bailiff of St. Albans near Basel, is 1102. This year is also considered the date of the founding of the city of Lörrach.