Grand Central Terminal Station 100th Anniversary, New York City, United States

- Covering Park Avenue
To accommodate ever-growing rail traffic into the restricted Midtown area, William J. Wilgus, chief engineer of the New York Central Railroad took advantage of the recent electrification technology to propose a novel scheme: a bi-level station below ground.
Arriving trains would go underground under Park Avenue, and proceed to an upper-level incoming station if they were mainline trains, or to a lower-level platform if they were suburban trains. In addition, turning loops within the station itself obviated complicated switching moves to bring back the trains to the coach yards for servicing. Departing mainline trains reversed into upper-level platforms in the conventional way.
Burying electric trains underground brought an additional advantage to the railroads: the ability to sell above-ground air rights over the tracks and platforms for real-estate development. With time, prestigious apartment and office buildings were erected around Grand Central, which turned the area into the most desirable commercial office district in Manhattan.