Somewhere beneath the feet of East Siders, a cavernous underworld of damp, rocky tunnels is slowly emerging. As part of the country’s largest construction project, thousands of unseen workers have been carving the tunnels for what will be New York’s new Second Avenue train. The line is slated for potential completion in 2019.

Last week the MTA unveiled a series of photos revealing the unrecognizable tunnels that  most New Yorkers know little about. First envisioned in the 1920s, the new T Train line and 7 Train extension would give Long Island Rail riders a direct route to Grand Central for the first time. This access will come through the creation of a new $8.3 billion hub–over half of the project’s projected $15 billion price tag. The MTA hopes it will alleviate crowding on the 4, 5, and 6 trains–a welcome improvement for east side commuters, for whom packing into the subway has become a rush hour ritual.

Two behemoth drills have ground day and night through rock with the help of dynamite to create these impressive engineered landscapes. “We’re using the best technology available today, but this is really people-intensive work,” said project engineer Michael Horodniceanu in a recent Huffington Post article. Workers are even controlling the temperature of the ground by freezing bedrock with special chemicals in order to increase stability.

“It’s not just about people going to work; the New York subway and rail systems are busy 24 hours a day, taking people shopping, to theaters, to clubs,” says director of the Rudin Center for Transportation Policy and Management at New York University, Mitchell Moss. The MTA hopes the new line will increase ridership while decreasing congestion in what is already the world’s most extensive subway system.

Check out more of the photos here.

Photos: MTA