From the 12th century Nuremberg Castle was the seat of the Burgraviate of Nuremberg. The burgraviate was ruled from about 1190 by the Zollerns, the Franconian line of the later House of Hohenzollern, which provided the German emperors of the 19th and 20th century. Under the Hohenstaufen kings, Conrad III and Frederick Barbarossa, Franconia became the centre of power in the Empire. During the time when there was no emperor, the Interregnum , some territorial princes became ever more powerful. After the Interregnum, however, the rulers succeeded in re-establishing a stronger royal lordship in Franconia. Franconia soon played an important role again for the monarchy at the time of Rudolf of Habsburg; the itineraries of his successors showing their preference for the Rhine-Main region. In 1376 the Swabian League of Cities was founded and was joined later by several Franconian imperial cities. During the 13th century the Teutonic Order was formed, taking over its first possession in Franconia in 1209, the Bailiwick of Franconia. The foundation of many schools and hospitals and the construction of numerous churches and castles in this area goes back to the work of this Roman Catholic military order. The residence place of the bailiwick was at Ellingen until 1789 when it was transferred to today's Bad Mergentheim. Other orders such as the Knights Templar could not gain a foothold in Franconia; the Order of St. John worked in the Bishopric of Würzburg and had short term commands.. Was the residence place of the bailiwick last at Bad Mergentheim or Ellingen?