Osaka Arsenal Chemistry Lab
The Osaka Arsenal (Ōsaka Hōhei Kōshō) was a sprawling complex of munitions factories located on the castle’s eastern side. Established in 1870 as Japan began to modernize its military, the arsenal produced a vast array of weapons and equipment, including much of the artillery used by the Imperial Japanese Army during World War II. At the peak of production, some 60,000 workers were employed here.
Large sections of the arsenal were destroyed by American bombing raids during the final days of the conflict, and most of what remained was later torn down. This structure, which housed a chemical analysis unit, is the only surviving building. After the war, it became a government office and later part of the engineering department of Osaka University and the provincial liaison office of the Japan Self-Defense Forces, who occupied it until 1994. The large chunk of iron slag nearby is believed to have been produced as part of the smelting that occurred at the arsenal.