Under the cover of night, 20 feet below ground, laborers excavated an eight-foot-wide, 300-foot-long tunnel in downtown New York City.
They worked for months in secret, and when it was finally revealed, the result was like something out of a Jules Verne fantasy.
Clean, fast, and luxurious - complete with sofas and even a grand piano and fountain stocked with goldfish - it promised to transform the future of public transit not just in Manhattan but around the world.
However, politics and crony capitalism killed the project before it had a chance to become more than just a curiosity.
Now - 155 years later - it is all but forgotten, marked only by a tiny brass plaque in a city apartment building.
