The work on our house has been going on for months, but we're finally starting to see a 'light at the end of the tunnel'.
The prisoners tried to 'tunnel' their way out. [=tried to escape by digging a tunnel]
His 'tunnel vision' made sensible discussions on political issues nearly impossible.
(..) ... the Ring passed out of all knowledge. Until,when chance came... ...it ensnared a new bearer. My precious. The Ring came to the creature Gollum... ... who took it deep into the tunnels of the Misty Mountains. And there it consumed him. It came to me. My own. My love. My own. My precious. (..)2001 The Lord of the Rings: The Fellowship of the Ring