The three towers are spaced in an equilateral triangle with sides of 300 meters, a design chosen to optimize transmission coverage.
Each tower weighs approximately 2,500 tons, with a base diameter of 12 meters.
The towers were built using a 'sliding formwork' construction technique, which was cutting-edge for the period.
The station was decommissioned for military use in 1997 but has been preserved as a heritage site.
The towers' resilience is often studied by engineers, as they were expected to last only a few decades but have survived for over a century.
The surrounding landscape is largely preserved to maintain the visual context of the original military installation.
It remains one of the few surviving large-scale radio transmission facilities from the Taisho period.
The Hario Transmission Station features three 136-meter-tall reinforced concrete radio towers built between 1918 and 1922. It is a designated Important Cultural Property of Japan, representing a significant milestone in early 20th-century wireless communication technology. The station played a critical role in the Imperial Japanese Navy's communication network, most notably transmitting the coded message 'Niitaka-yama Nobore 1208' that ordered the attack on Pearl Harbor. The site served as a vital communication hub for long-distance transmissions across the Pacific. The towers were constructed using an innovative method that allowed for rapid casting of concrete in a continuous sequence. Despite their age, the towers remain structurally intact, defying initial concerns regarding the durability of early concrete structures. The facility is located in Sasebo, overlooking Omura Bay. It serves as a reminder of the strategic importance of the Nagasaki region in Japanese military history.
The viewing area from the adjacent park grounds offers the best perspective to frame all three towers simultaneously.
Bring comfortable walking shoes to navigate the gravel and earthen paths around the base of the towers.
Check the weather before visiting, as the site is fully outdoors and exposed to coastal winds.
Bring a wide-angle camera lens to capture the full height of the towers from the ground.
Do not attempt to enter the fenced off-limits military zones that may border the historical site.
Closed during inclement weather and potentially on designated local holidays.
Stay within the designated visitor paths and do not attempt to climb or touch the tower bases.
