The tunnel info center was really neat.  The structure (glass, on the left) hung from beams in...

The tunnel info center was really neat. The structure (glass, on the left) hung from beams in the ceiling, which were supported on exterior walls of riprap (right). The riprap is all crushed rock from within the tunnel itself.

Location
SwitzerlandGotthard Base Tunnel
Photographer
Catherine Hovell
Date taken