 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 (1254–1273), some territorial princes became ever more powerful.