The Caverns Under Manhattan: Stunning Images of 2nd Ave. Subway Tunnels (Photos)

It was proposed in the first half of the 20th  century to reduce congestion on the already inundated Lexington Avenue  line.
And decades later, after decades of red tape,  the Second Avenue subway is taking form.

In a series of photos posted by the  MTA, deep caverns can be seen

These stunning pictures provide a unique look  into the caverns below Manhattan’s Upper East Side, as workers below burrow,  build, and blast the subway line into existence.

The MTA workers are busy at work hundreds of  feet below the surface of Manhattan; these intriguing photographs show the  progress along the northern reaches of the line, from 96th St to 63rd  St.

The 63rd St Station is being expanded to  accommodate the new trains; as it stands, the F train stops at the station right  before it passes into Queens.

Photographs show MTA workers in orange vests  sawing plywood and welding metal at the station, which still looks quite  skeletal, though signal switches have been installed, as well as a few famous  Helvetica-scripted signs.

One stop north at the 72nd St Station, the  construction is in a more infant — and messy — state. One picture shows a small  work shed next to a very muddy platform. Crews are currently working on covering  the raw bedrock of the expansive cavern.

Bright yellow tarps can be seen throughout  the station covering the top of the cavern.

The unique bedrock of the island is both a  blessing and a curse to crews, as it is remarkably tough, providing the perfect  foundation for tunnels, but also making it a laborious task to barge  through.

Construction of the subway was put off by one  thing after another, as world events like the Great Depression and World War II  threw a wrench in the city’s plans.

Planning for the current SAS line began in  2004, with the groundbreaking happening on April 12, 2007. When complete, the  line will run from 125th St in Harlem, down through the Upper East Side,  Midtown, downtown, and terminating in the Financial District at Hanover Square.

It will serve to reduce congestion and  dangerous overcrowding on the Lexington Avenue line, which typically runs  at  120 percent capacity.

When completed, the line will likely be  designated the letter T, and designated a turquoise color.