The Nightingale floors: A Japanese flooring system which was used for catching intruders

Nightingale floors, also known as “uguisubari” were a type of flooring system designed to sing when someone walked upon.

Used in the hallways of palaces and temples, these floors make a chirping sound similar to songbird’s chirping that alerts the guards of the buildings and forces the intruder to flee from the site. The English name for Nightingale refers to the Japanese bush warbler bird or uguisu. So, “uguisubari” in translation from Japanese means “bush warbler guard watch.”

A close-up of the mechanism in the nightingale floor at Chino-in temple

The most famous example of Nightingale floor can be seen in the Nijo Castle in Kyoto, Japan. It was made in the Ninomaru Palace which is part of the castle located in the Outer Ward. According to the Japanese mythology, these floors were made that way so that the guards could defend the place from ninjas. The ninjas had a very quiet approach, so these designs were made to reveal even the most silent steps.

The Nightingale floors at Eikan-dō Zenrin-Ji 

Many of these floors were installed to safeguard the temple’s treasures. The Nijo Castle was built during the Edo Period, and it was the main seat of Japan’s power where many military commanders stayed. It is said that the Nightingale floor still functions today and it was used to protect these very important guests.

The floors make a chirping noise when they are under pressure

It is said that when Shogun or Daimyo Commander visited the castle, some of their rooms had special doors where their bodyguards stayed and waited for attackers to walk through the floors. This automated intruder alarm was invented by the best craftsmen, woodworkers, and carpenters in Japan.

The Ninomaru Palace at Nijo Castle 

According to Rocket News 24, in installing nightingale floors, planks of wood are placed atop a framework of supporting beams, securely enough, so they won’t dislodge, but still loosely enough that there’s a little bit of play when they’re stepped on. When the feet of the intruder press down the boards, the clamps of the floor rub against the nails which are attached to the timbers and make the famous chirping noise.

It is a unique timber technique that could even be used to help pinpoint the right position of the intruder by the size of the noise. Besides Nijo Castle, Nightingale floors can be found in the Chion-in temple in Higashiyama-Ku, Eikan-do-Zenrin-Ji temple, and the Shingon Buddhist temple, Daikaku-Ji in Kyoto.

The Chion-in Temple

Today, many visitors come to these places to step on these alarm floors and record audio of their chirping sounds. There is an audio recording from the Daikaku-Ji temple which can be heard on Wikipedia in the article for Nightingale floor.

(Source: The Vintage News)