Behind the majestic design and décor of Grand Central Terminal is a triumph of engineering and ingenuity. Grand Central didn’t just do things better than other train terminals. It did them differently. It pioneered new approaches to organizing space. It invented new technologies. And it overcame the daunting challenge of building a vast, durable, efficient train station—much of it buried deep underground—in the bustling center of the nation’s busiest city. More and more people were riding more and more trains. Grand Central needed additional tracks…and efficient ways for passengers to reach those tracks. With little space to spread out, the station dug down. Engineers created a vast underground structure: four tracks in the Park Avenue tunnel and a 123-track train shed designed to support heavy locomotives plus the weight of the buildings overhead. A series of crossovers let trains reach any platform from any track. Inside the station, meanwhile, pedestrian ramps took passengers swiftly from level to level. The design also included a centralized hot water heating system—the largest of its kind at the time—with four miles of pipe serving the station and surrounding buildings.

Destroyed trolley after an explosion near the Grand Central Terminal Powerhouse at 50th Street between Park and Lexington Avenues, December 1910. On December 19, 1910 an explosion at the New York Central Railroad's Sub Station killed 13 people and injured dozens of others. At 8:22 A.M. the massive explosion (likely two blasts, one from a gas issue and one from the dynamite kept in the still-being completed powerhouse) rocked the area. The blast threw up brick, stones, beams, and other building materials, tossing them hundreds of feet. Windows in the area were blown out and a passing trolley felt the brunt of the force, killing at least four passengers.