First of all I'll apologise if this particular train has been featured here previously...
A couple of years ago I was travelling to a hot spring resort south of Tokyo. Part of the journey there involved switching to a local service train. It took a coastal route and passed through many tunnels along the way.
The train was a special sightseeing service. It has fully adjustable seating, large windows and something special each time we entered a tunnel...
In the darkness the ceiling became an animated scene of the cosmos with twinkling stars, meteors, etc.
I discovered after the trip that it was named a 'Black Ship Train' and operates only on this route. Here is some film I took of the journey through a tunnel.
http://www.youtube.com/v/vCW-zOPVpAgHere are more images from someone else's experience on the train:
http://m-imajo.main.jp/m-imajo/akari/akarimuseum/folder3/izukyukurofune-e.html