Just in front of Palaceside Building in Takebashi, Tokyo, on the lawn of the former Edo Castle main keep in the East Gardens of the Imperial Palace, stands a stone marker reading "Site of the Noon Gun Platform." A cannon platform once fired the noon signal. The noon gun was institutionalized in October 1871 (Meiji 4) under the Noon Gun System; blank shots at noon told towns across Japan the hour. From the sound, it was commonly called "Don."
In Tokyo the platform was on the drill ground next to the Central Meteorological Observatory in the main keep; the Imperial Guard fired it, then the Navy School and others took over, and in 1922 (Taisho 11) the military withdrew for budget cuts and Tokyo City took charge. Though nearby residents complained of noise, it was known as "Marunouchi's Don" and loved by citizens. On May 1, 1929 (Showa 4), blank shots ceased for financial reasons and sirens at various city locations replaced them. The actual "Marunouchi's Don" is preserved at Edo-Tokyo Open Air Architectural Museum in Koganei, Tokyo.
Noon gun platforms are studied and preserved nationwide.
Among them, "Okayama's Don" deserves special mention.
Okayama's platform was set up in 1908 (Meiji 41) on Handa Mountain north of the city by the 17th Division; the Okayama Mountain Artillery operated it, but the unit was abolished amid force reductions and the noon gun fell silent on August 15, 1922 (Taisho 11). Okayama City then continued until March 1929.
After the war the site on Handa Mountain became an illegal dump, but students at Kake Gakuen Okayama University of Science High School, saying "We cannot leave this precious historic site as it is," launched an excavation. Working with Okayama University of Science under Professor Shuichi Kameda, students cleared trees and illegally dumped waste and unearthed wheel chocks and drains.
Meanwhile, mechanical-course students at the high school worked to restore the cannon that fired the noon gun. After visiting foundries and museums, they drew plans from photos in local newspapers and cast parts of the gun and carriage in aluminum. Assembly used rivets, not welding; painted bronze to match the real gun, they completed a replica unveiled in December 2009 (Heisei 21) on Handa Mountain, where it still overlooks Okayama City.