The demolition of the original Penn Station helped catalyze the modern historic preservation movement, and the lessons of that movement guided the creation of Moynihan Train Hall. Rather than treating the interior of the Beaux-Arts Farley Building as a blank slate, the project team developed a modern rail hub that celebrates the historic, landmarked building.

Moynihan Train Hall reverses the dark, overcrowded experience that so many commuters have endured for decades. Its main concourse is situated in the former mail sorting room, a previously sky-lit space that was shrouded during World War II. Today, a new skylight traverses this concourse – bringing sunlight back inside while reclaiming the magnificence of the original, sky-lit Penn Station. The new ceiling is composed of four catenary vaults, each of which comprise more than 500 glass and steel panels that create a moiré effect. At the edges of each vault, the panels thicken to sustain greater structural loads, while at the apexes, which rise 92 feet high, the panels' depth lightens to enhance the airy ambience of the space.

Three massive, original steel trusses, which were invisible to the postal workers a century ago, were uncovered to become a focal point of the design. As the framework for the new skylight, the bolted trusses enhance the sense of lightness within the Train Hall – seamlessly combining a contemporary architectural element with the workmanship of the original structure.

Moynihan Train Hall is accessible through a variety of grand entrances on Eighth Avenue, 31st Street, 33rd Street, and Ninth Avenue. Along 31st and 33rd Streets, new mid-block canopies help identify the civic presence of the Train Hall and complement the original arched windows of the Farley Building, and public art installations by artist duo Elmgreen & Dragset and artist Kehinde Wiley greet visitors inside. In the center of the mid-block passageway, between the murals, a second skylight maintains the essence of the main concourse. Throughout the interior, carefully selected materials unify each space, with Tennessee Quaker Gray marble—the same stone used for Grand Central Terminal—lending to Moynihan Train Hall a sense of serenity and grandeur.