1. Tomioka Silk MillTomioka Tomioka Silk Mill is Japan's oldest modern model silk reeling factory, established in 1872 by the government to introduce modern machine silk reeling from France and spread its technology in Japan. The factory is designated by the government as a historic site and all its buildings are preserved in very good condition. It is a big factory in the old city of Tomioka, in Gunma prefecture, Japan — about 100 km northwest of Tokyo. From Wikipedia, the free encyclopedia.