The story unfurls along the West Side of the city’s hallowed underground cartography, more than 30 years after a zealous band of mapmakers first converged to reimagine New York’s sprawling jigsaw of subway lines.

Their task was formidable: devise a modern guide to replace the old map, designed by Massimo Vignelli in 1972 with an artist’s touch but a less-than-faithful adherence to the city’s true geography.

Success was claimed. Credit was fought over. Feelings were hurt.

And now it can be told: Mistakes were made.

On the West Side of Manhattan, beginning near Lincoln Center and extending toward the campus of Columbia University, Broadway is seemingly misplaced. It is west of Amsterdam Avenue at West 66th Street when it should be east. It drifts toward West End Avenue near 72nd Street, where it should intersect with Amsterdam. It overtakes West End Avenue north of the avenue’s actual endpoint near West 107th Street, creating several blocks of fictitious Upper West Side real estate.