A very quiet town, unazuki-onsen is where you go to get to Kurobe Gorge. It takes about 4 hours to get there from Tokyo with a change at Echigoyuzawa and Uozu. You also have to top up JPY1300+ towards Uozu because the train travels on non-JR line. Then you cross to the Shin-Uozu station to take a train to Unazuki-onsen, it’s non-JR.
You then cross over to the Kurobe Tram station to board to tram to enter the gorge. Round-trip takes 3 hours. Basically you just sit on the tram and enjoy the scenery =) which I feel is nicer than Taroko Gorge in Taiwan. Take the cheapest most open carriage if you can stand the cold winds or the second cheapest which has windows so it’s not so cold. You can enjoy outdoor hot springs at Keyakidaira or Kanetsuri. I suggest at least one hour at Keyakidaira if you want to soak in the hot spring and more if you wish to eat there (we saw some udon shops).
During Summer holidays and Autumnal colours, the place is very crowded so making reservations (via your hotel for example) for train tickets is advisable. Here's the fare and time table.