From late-April to the end of June, you can see humongous, ten-meter walls of snow near the top of Mt. Norikuradake. Walking between these towering white walls of winter is quite an experience and on a clear day, you can see the mountains of Nagano far and wide spread across the horizon. Get there by taking a bus from Norikura Kogen Tourist Information Center. After getting off the bus, you can walk around and enjoy the scenery. It’s very cold up here, so you want to bring warm clothes, especially in early spring which will feel like winter at the top of the mountain. When you have finished looking around, take the next bus back down to the visitor center. Another option is to walk back down the road yourself about 3.5 kilometers to Kuraigahara Sanso (a mountain lodge), where you can grab a bowl of hot noodles and then take a bus from there. You could also walk all the way back to the Norikura Kogen Tourist Information Center, but it is a long 18 kilometer trek that would take around 4–5 hours (in that case, make sure you start early because you do not want to get stuck on the mountain after the buses haves stopped running!)
First, you need to get yourself to the Norikura Kogen Tourist Information Center (bus stop number: K-29) by taking a bus from Shin-Shimashima Station (K-01) or driving. From the visitor center, you have to take the Haruyama Bus up to the Daisekkei (Snow Gorge) bus stop (N-40). Please note that you cannot drive up to the snow walls yourself. Buy the ticket at the visitor center (get a round-trip ticket if you plan on riding the bus back down because its cheaper).
The bus timetable is here.