Seikan tunnel is connected between Honshu island and Hokkaido and the total length of the tunnel is 53.85km.
The tunnel is second longest one at present.
You can see Shinkansen go in and out of the tunnel at the park.
There are shop, toilet, parking and observatory at the park and you can check the passing time of Shinkansen at the shop.
We recommend that you visit here morning(10-12AM) and late afternoon(3-6PM), if you see the train definitely.