the name came from the manganese mine the palace had been built on top of over a thousand years ago , and rumor had it that the old mining shafts served as an escape route for the emperor in or out of the palace in case of trouble ; there was a famous story about how the late emperor dennokk , the father of the sitting monarch , had been ushered into the caves during a mass riot on an urkuran that had been just as tense as this one .