In New York City, an 800-foot long, two-story-tall tunnel-boring machine is drilling the long-awaited Second Avenue Subway Line that has been 75 years in the making. Wired Science takes you underground to see the project up close.

<img src="https://feedads.g.doubleclick.net/~at/zf6tsrIEfcANkuISIBts-5U8lH0/1/di"