The Old Maruyama Transformer Substation is a brick building constructed in 1912 as a transformer substation to supply electricity to trains going over Usuitoge Pass. It has been designated along with Megane Bridge as a National Important Cultural Asset.
The Usui Line was a main railroad line in Japan and was the first line to be electrified with the inside of the substation containing machinery and secondary batteries which amassed cutting-edge technology of the times in Japan. The architecture which suddenly appears in the middle of the mountains absorbed the Western culture of the Meiji and Taisho eras as the fruits of labor by people who were trying to develop the nation, showing its grand appearance.
|Business hours||Open all day（entrance into the building itself is prohibited）|
|Address||旧丸山変電所 Matsuidamachi Yokokawa, Annaka, Gunma Prefecture 379-0301|