Canada - Spiral train tunnels

They've made a nice little tourist attraction here with information boards and a great viewing platform.
We were very lucky as a train arrived very shortly after our coach dropped us off!
 

Here's the train track just to the left of centre.
 

There...
 

The tunnels were built to overcome the steep gradient of the track.
The train enters the mountain, loops round inside the mountain, and emerges some feet below the entrance tunnel.
Here's the train entering the tunnel...
 

Here's the train leaving the lower tunnel exit.
 

As the train can be two miles long it can be seen entering the tunnel at the top as well as leaving the tunnel at the bottom! Amazing.