It’s taken 100 years to build the city of the future.

Though dreamed of for decades, the transformation of Manhattan’s West Side is coming to pass in the Hudson Yards district, an ambitious public-private initiative launched under former New York City Mayor Mike Bloomberg.

“It’s about 35 blocks that was essentially Manhattan’s last frontier,” Dan Doctoroff, the former deputy mayor under Bloomberg, tells Business Insider.

One section, over the still-active rail yards, is a private development being led by billionaire Steve Ross. His Related Companies is overseeing the Hudson Yards project, which spans 28 acres, from 30th to 34th streets and from 10th Avenue to the Hudson River.

As conceived, it will be a state-of-the-art showcase of technology, science, engineering, and design.

"The project it's most often compared to is Rockefeller Center in the '30s. It's bigger than Rockefeller Center," Jay Cross, president of Related Hudson Yards, tells Business Insider.

"It's the biggest private development in the history of the US. We're going to be at $25 billion by the time we're finished, and I don't think there's anything that comes close to that," Cross says.

Business Insider gained exclusive access to the construction site with our 360 cameras. Here, we tell the story of how Hudson Yards came to be, and what it promises for New Yorkers by the time it's finished - in 2025.

Producer: Diane Galligan

Camera and editing: Steve Johnson; a dditional camera: Alana Kakoyiannis

Graphics: Keegan Larwin

Narration: Will Wei