The Nijo Palace in Kyoto has special floors that squeak when walked upon, a sound that is very similar to the Nightingale birds. So when attackers tried to kill the Shogun, they would give their position away, but would only think that the birds outside are chirping.
“Nijo Castle (二条城 Nijō-jō?) is a flatland castle located in Kyoto, Japan. The castle consists of two concentric rings of fortifications, the Ninomaru Palace, the ruins of the Honmaru Palace, various support buildings and several gardens. The surface area of the castle is 275,000 square meters, of which 8000 square meters is occupied by buildings.
The 3300 square meter Ninomaru Palace (二の丸御殿 Ninomaru Gōten?) consists of five connected separate buildings and is built almost entirely of Hinoki cypress. The decoration includes lavish quantities of gold leaf and elaborate wood carvings, intended to impress visitors with the power and wealth of the shoguns. The sliding doors and walls of each room are decorated with wall paintings by artists of the Kanō school.The castle is an excellent example of social control manifested in architectural space. Low-ranking visitors were received in the outer regions of the Ninomaru, whereas high-ranking visitors were shown the more subtle inner chambers. Rather than attempt to conceal the entrances to the rooms for bodyguards (as was done in many castles), the Tokugawas chose to display them prominently. Thus, the construction lent itself to expressing intimidation and power to Edo-period visitors.The building houses several different reception chambers, offices and the living quarters of the shogun, where only female attendants were allowed. One of the most striking features of the Ninomaru Palace are the “”nightingale floors”” (uguisubari) in the corridors. To protect the occupants from sneak attacks and assassins, the builders constructed the floors of the corridors in such a way as to squeak like birds when anyone walks on them.Some of the rooms in the castle also contained special doors where the shogun’s bodyguard could sneak out to protect him.The room sequence starting at the entrance is:Yanagi-no-ma (Willow Room),Wakamatsu-no-ma (Young Pine Room)Tozamurai-no-ma (Retainers’ Room)Shikidai-no-ma (Reception Room)Rōchu-no-ma (Ministers’ Offices)Chokushi-no-ma (Imperial Messenger’s Room)The Ōhiroma (Great Hall) is the central core of the Ninomaru Palace and consists of four chambers:Ichi-no-ma (First Grand Chamber)Ni-no-ma (Second Grand Chamber)San-no-ma (Third Grand Chamber)Yon-no-ma (Fourth Grand Chamber)as well as the Musha-kakushi-no-ma (Bodyguards’ Chamber) and the Sotetsu-no-ma (Japanese fern-palm chamber).The rear sections are the Kuroshoin (Inner Audience Chamber) and Shiroshoin (Shogun’s living quarters)The main access to the Ninomaru is through the karamon, a court and the mi-kurumayose or “”honourable carriages approach