[malikolivier]

Driving through these roads just after they open around March/April is a blast. If you look enough, you can find places where you can actually climb on the snow walls and ski/hike on the snow slopes yourself. You may see a few trees whose apex is slightly protruding from the snow. It really feels like walking on the forest's canopy.

Apart from the road mentioned in this article, which I believe is the Tateyama Kurobe Alpine Route, you have the Shibu-touge (渋峠) road, which crosses the mountains between the Nagano and Gunma prefectures [1].

The Tateyama Kurobe Alpine Route does not allow private traffic on it year-round: it is a bus/taxi-only road. So if you are driving on your own, Shibu-touge is a great alternative. Route 299 going through the Yatsugatake (八ヶ岳) mountains is another alternative [2], although less fun in my opinion.

[1] https://goo.gl/maps/YbsoEgvih4oG3xvX9

[2] https://goo.gl/maps/nJB26wo6YzPVcawH9