Complex sentence: Until the 17th century, Plassenburg was the residence of the burggrave office or "Amt", later the "Amt" of the Hohenzollern Principality of Kulmbach (also: "Brandenburg-Kulmbach" or, after 1604, "Brandenburg-Bayreuth").
Split into simpler sentences: Until the 17th century, Plassenburg was the residence of the burggrave office or "Amt". Later it was the "Amt" for the Hohenzollern Principality of Kulmbach (also: "Brandenburg-Kulmbach" or, after 1604, "Brandenburg-Bayreuth").