Known affectionately as Bertha, this tunnel boring machine has the widest diameter of any boring machine ever built; 57.5 feet. It's being used to dig a highway tunnel under downtown Seattle and it just arrived there today after being shipped from Japan.

I feel this warrants your attention for two reasons:
1) If you live near Seattle, you can actually go get a look at this massive beast before it starts chewing its way through the city. If you like looking at giant machines (or know someone who does) now's your chance. She's coming into the Port of Seattle, Terminal 46, as you read this and there will be ample opportunities to get a look as the pieces are assembled and moved into the nearby launch pit. The Washington State Department of Transportation has suggestions on places to go to get a good view.
2) If, for some reason, you were looking for a new way to lose massive amounts of time on YouTube, Bertha (and boring machines, in general) can help with that. Here's a cutaway animation explaining how boring machines work. Here's a video of Big Becky, another boring machine, breaking through to the other side of a tunnel at Niagara Falls, Canada. (In fact, boring machine breakthrough videos are, in and of themselves, a mesmerizing genre.) And in this video, you can watch the massively long line of support equipment go by in the wake of a boring machine.