NEW YORK (CBSNewYork/AP)– The largest and most expensive piece of real estate development in U.S. history is now under construction on the West Side of Manhattan.

Developers on Wednesday unveiled what the centerpiece of Hudson Yards will look like. They call it “vessel.” And it is made of 154 interconnecting flights of stairs that visitors can climb and then view the public square and gardens below.

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The centerpiece comes from British designer Thomas Heatherwick and is an inverted honeycomb-like structure of platforms and stairways that will stand 150 feet high. Heatherwick’s other projects include the cauldron for the 2012 Olympics in London.

The space will also include 28,000 plants and more than 200 mature trees. The public space will connect to the High Line and the new Hudson Park and Boulevard.

Mayor Bill de Blasio said the work symbolizes the constant evolution of New York.

“Hudson Yards is re-energizing a section of our city that not long ago was disconnected from the vast majority of us,” Mayor de Blasio said. “Something is happening here that is opening up vast potential.”

But there is a lot more to the development than the centerpiece. The whole project is quite an architectural feat in both scale and concept.

Last week, CBS2’s Kristine Johnson got an exclusive tour of the rest of the massive real estate undertaking from the man behind it.

Hudson Yards is located at the site of a train depot known as the West Side Rail Yard, and it’s considered some of the most coveted real estate in Manhattan.

“This is going to be the place where people want to be,” said developer Stephen Ross.

Ross believes the area will soon replace Rockefeller Center as the heart of New York City.

“New York is growing,” Ross said. “If you don’t allow a city to grow, it’s going to die.”

To bring life to the area, Ross hired a team of renowned architects – “starchitects” as he calls them – to design each structure individually.

Their vision will transform the landscape and skyline of New York City.

“I think the live, work, play environment is so important today,” Ross said.

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He said Hudson Yards will be a place where companies will relocate, New Yorkers will live, and tourists will visit.

“You have the High Line coming right into the project,” Ross said.

In addition to the High Line, the area is also hugged by the Jacob Javits Convention Center and is the site of a brand new subway station.

But the rail yard must stay – so Ross is building over it.

“This is like the largest project ever done in the United States, so it’s really building a city within a city, you know, on a place that probably people thought wasn’t possible,” Ross said.

So how does one build a city within a city on top of an existing rail yard? The plan will involve a concrete platform supported by 300 pillars.”

“We want this to be the best in class — the best development ever done,” Ross said.

Ross said no expense was spared. When the 20 million square-foot development is complete, it will include state-of-the-art office buildings, 100 premiere shops and restaurants, 14 acres of open space, a hotel, a school, and approximately 4,000 apartments that people will call home.

“I think the goal of any developer is something that is impactful and transformative,” Ross said.

Ross makes rebuilding a city sound so easy — perhaps because for him, it’s a true labor of love.

“This is like living the dream,” Ross said. “It’s not about how much money you make. It’s about the kind of legacy and what you do for the city because this is going to be here forever.”

Ross says his ultimate goal is to bring this concept of a “sustainable neighborhood,” where people live, work and play, to cities around the world.

One of CBS2’s Johnson’s favorite elements of the project is the open-air observation deck on top of 30 Hudson Yards, which will be the highest observation deck in the city. The building will be taller than the Empire State Building.

Hudson Yards is scheduled to be complete in 2025 with a final price tag of somewhere around $20 billion.

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