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Ancient alarm in the palace of the Emperor of Japan
In the former capital of Japan, Kyoto, the ancient imperial palace is one of the attractions which is the nightingale floor ("uguysu MIS"). Boards that make up the floor, connected to the metal, so while walking on it, you can enjoy the melody, reminiscent of the singing nightingale. This design also act as signaling that nobody was allowed to sneak into the rooms of the emperor.