Banpingshan Tunnel Factories (6th Naval Fuel Depot Remnants)

The Banpingshan Tunnel Factories are a set of three underground industrial caverns excavated into the southern slope of Half-Screen Mountain (半屏山), located at the boundary of Zuoying and Nanzi Districts in Kaohsiung. They were built as emergency wartime facilities for the Imperial Japanese Navy's 6th Naval Fuel Depot (第六海軍燃料廠).

The 6th Naval Fuel Depot was established at the foot of Banpingshan to produce aviation fuel, lubricants, and other petroleum products essential to the Japanese war effort. It completed construction of two crude oil distillation plants in 1944, making it one of the most strategically important industrial targets in Taiwan.

As US air attacks on Kaohsiung intensified from October 1944 onward — beginning with the carrier raids of the Formosa air battle — the above-ground refinery facilities were damaged and production was repeatedly halted. In response, the Japanese Navy mobilized civilian labor to excavate tunnels into Banpingshan's limestone, planning to relocate critical refining equipment underground. Three tunnel complexes were carved into the south slope: the 'Oxygen Production Factory' (酸素工場), the 'Machine Works Cavern' (工作機械洞窟), and a third support tunnel. Main tunnels (designated No. 8 and No. 9) each extended approximately 60 meters with widths and heights of about 6 meters.

The tunnels were sealed after Japan's surrender in August 1945. They lay forgotten for over half a century until October 2002, when construction crews building an access road for the new Zuoying High-Speed Rail Station accidentally broke into the tunnel system. Some sections were unfortunately destroyed before their historical significance was recognized.

In December 2017, a separate exploration confirmed the existence of a sealed underground reservoir inside the mountain — a tunnel-shaped emergency water store more than 100 meters long, built by the Japanese Navy around 1943 — that had been the subject of local legend for decades. The entrance to the main tunnel complex is located near the Banpinghu Road (半屏湖路) signpost, where an abandoned guard post marks the former entrance.