It's a fascinating place: kind of at the crossroads of the major far east powers, which means depending on who held the upper hand militarily at the moment, they marched in and kicked the other guy out.
The Russians took it from the Japanese in 1945. The Japanese took it from the Russians 40 years before.
We were in Yuzhno-Sakhalinsk, the capitol city. The Soviets doing business the ways the Soviets did, when they marched into Toyohara (The Japanese name) they tore down every building but the governor's palace, rebuilt with Soviet buildings, established Lenin square, and gradually shoved the Japanese residents onto boats headed for Hokkaido when mainland Russians showed up to take their place (most of whom didn't really want to move there...). There were many Koreans there who the Japanese brought as slave labor to work the coal mines. The Soviets wouldn't let them go. After the end of the Soviet Union some of their descendants tried moving to South Korea and found they weren't really at home there either.
It's like Hokkaido: very mountainous and quite beautiful.
I would loved to have seen the railroad run, but we were there as part of a group and not allowed to run loose. All I could do was press my face against the window whenever we drove across a crossing!
It was obviously some kind of narrow gauge, but I didn't find out until I got home and Googled it!