Why did we want to come down to the railway line here?
To do the Tunnel 25C of course.
We used the service tunnel located near the entrance of Tunnel 25 visible in the earlier picture to enter the 25C. The service tunnel has a concrete floor now. It intersects the 2 Km long Tunnel 25C at almost the halfway mark.
The service tunnel was used during the construction of the 25C to transport material; today it serves as an outlet for the water that has collected on both sides of the line inside the tunnel. The service tunnel has importance from the point of view of disaster relief in the event of a mishap inside the Tunnel 25C.