The biggest transportation project in the country is being built deep beneath midtown Manhattan, but after years of construction, it finally will become visible to New Yorkers. NY1's Jose Martinez filed the following report.

It's the MTA's stealth project: a cavernous $10 billion train station known as East Side Access taking shape out of sight, deep beneath bustling Grand Central Terminal.

"While we were blasting downstairs - and we blasted a lot - people in the Grand Central were sipping a glass of wine without knowing that we were ever there," said Michael Horodniceanu, president of MTA Capital Construction.

But no more. On Tuesday, officials posed for a ceremonial groundbreaking on the lower level of Grand Central, giving the public its first real sense that something very big is going on downstairs.

The ceremony heralds the construction of a passageway linking the century-old terminal to the new train station, which will bring Long Island Rail Road service to the East Side for the first time.

"Someday, we'll be here cutting a ribbon, but this is a milestone and a step to get there" said Pat Nowakowski, president of the Long Island Rail Road. "And the thought of our riders having that choice, of destinations either on the East Side or West Side, is something that they've long looked for."

MTA officials say the East Side connection will cut travel times for tens of thousands of LIRR riders who work on the East Side by as much as 40 minutes. It also has big implications for the agency’s other commuter railroad.

"East Side Access is enabling Metro-North to undertake our first major expansion, which is the contruction of four new stations in the Eastern Bronx and the start of service to them, with trains operating on the New Haven line to and from Penn Station," said Joseph Giuletti, president of Metro-North.

More than 100 tables and chairs in Grand Central's food court had to be relocated so work could begin on the passage to the East Side Access.

Forty-seven escalators and 22 elevators eventually will be installed so riders can reach the new, and very deep, terminal. How deep? Officials say it could take three to four minutes to reach the street from the deepest of the new LIRR platforms.

For all the MTA’s recent show-and-tell efforts, the new terminal isn’t expected to open for a while, not until at least December 2022.