There were two different lines until the opening of the Shinkansen line. It has a maximum incline of 66.6 permille and is one of the steppest in Japan. Today there is a museum. The EF63 will be included. The line is setted in the early 90's when trains drove on it. It goes from Karuizawa to Yokokawa around 20km.
Added as a (second) duplicate to the Shin'etsu Main Line suggestion in the list of Japanese route suggestions, as linked in my signature. If I understand correctly, this is the same route as the other two in the list.
