The Robertson Tunnel in Portland, Oregon

A part of the MAX mass transit line, it's actually a double tunnel with two trains passing through at a single time, funneling under a huge hillside and connecting suburban Portland to the downtown core.

It's almost 3 MILES long and reaches a maximum depth of 300 feet under solid basalt rock to the deepest subway tunnel in the United States.

Here's a picture of the route. It cuts down a 20 minute drive to exactly 5 minutes, with the trains going at a constant rate of 55 miles per hour. And it's NEVER late.

The twin tunnels, 21 feet in diameter, were bored with this machine over the course of six years through 16 million year old solid basalt rock.

The trains enter the tunnel from the east end here. This pleasant location is Washington Park, located a two-minutes walk from downtown Portland.

It then exits on the west side here. Notice how well it blends with the surrounding forest.

The tunnel has had some interesting incidents. Recently, someone drove their car onto the tracks and fairly fair into the tunnel. Crews then had to take it out, delaying service for half an hour, one of the few times ever that service has been delayed.

It is truly a very cool project, and one that is not often highlighted as well.