The Imperial Castle of Kyffhausen (German: Reichsburg Kyffhausen) is a medieval castle ruin, situated in the Kyffhäuser hills in the German state of Thuringia, close to its border with Saxony-Anhalt. Probably founded about 1000, it superseded the nearby imperial palace (Kaiserpfalz) of Tilleda under the rule of the Hohenstaufen emperors during the 12th and 13th centuries. Together with the Kyffhäuser Monument, erected on the castle grounds between 1890 and 1896, it is today a popular tourist destination. The castle is variously known in English as Kyffhausen Castle, Kyffhauser Castle, Kyffhäuser Castle, and Kyffhaueser Castle.