The Big Dig Tour / Tunnel Construction 2K. M. Peterson
This is further into the tunnel. This section is "newer" (and hence, less finished) than the previous. There's significant work underway on the walls here, and you can see a large steel girder ahead that is in the process of being removed (it's a temporary support while the excavation is being completed but is no longer necessary when the tunnel pour is complete).
There's about 15' (4.5m) of concrete below us.