The builders of Japan’s Nijo castle created purposefully squeaky floors, known as nightingale floors, to prevent ninja assassins from sneaking in. The floors were designed so that just the lightest step produced a clearly audible sound warning guards. – WTF Fun Facts
Source: https://www.amusingplanet.com/2018/04/nightingale-floor-ancient-japanese.html
WTF Fun Fact – Nightingale Floor
