The James A. Farley Post Office building is one of Manhattan’s most storied structures: It was completed in 1913 by the office of McKim, Mead & White, intended to complement the firm’s grand Penn Station, which was located across the street. In 1966, after the demolition of the majestic old train hall, the Farley building became one of the first structures to gain protection under the city’s new Landmarks Law.

And through it all, it’s served as a post office, with a quote from Herotodus—“Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds”—inscribed across its Eighth Avenue facade.

But soon, the Farley building will take a different form: A large portion of the building is being gutted in preparation for its transformation into the Moynihan Train Hall. Construction on the new transit hub began a year ago, and during a press conference-cum-campaign event about a new entrance to Penn Station, Gov. Andrew Cuomo announced several milestones for the project—namely, the fact that the structure for its enormous skylight has been installed, and the first glass panel for that architectural feature has been placed.

Representatives from Empire State Development, the state agency overseeing the train hall revamp, recently led a tour of the building, which is largely a construction zone. The current post office, just off of Eighth Avenue, is still active; but behind it, hundreds of workers are busy ripping out the guts of the building, and adding in new escalators, a large mezzanine, and other 21st-century features.

Historic elements—including terra cotta tiles, arched windows, and its massive colonnades—will also be preserved in the new station.

When it’s completed in 2020, the Moynihan Train Hall will connect to the current Penn Station, offering new access points, more tracks, and a less claustrophobic waiting area for commuters. The total cost of the project, $1.6 billion, is being shouldered by several different agencies and private entities, including the MTA, Amtrak, and a cohort of developers (Skanska, Related, and Vornado).

There have also been piecemeal improvements at the current, much-maligned Penn Station: The West End Concourse, which connects Penn to a new subway entrance below the Farley building, opened in 2017. And a new 33rd Street entrance and pedestrian plaza on that block, announced by Cuomo yesterday, are now also in the works—though it’s unclear who will be designing that, and how it will be funded.