The head of Zaha Hadid’s firm is not impressed by One World Trade Center — and he bluntly said so in front of a partner who works for the firm that designed it.

“[It’s a] sterile, blind, self-disappearing piece that’s nothing,” Patrik Schumacher said during a panel on Friday. “Although there were unbelievably prescient and potent concepts on the table … instead we ended up with this piece.”

As he talked smack, Schumacher shared the stage with Roger Duffy, a design partner at Skidmore, Owings & Merrill — the firm that designed the $3.8 billion skyscraper. Duffy didn’t visibly react to Schumacher’s remarks, despite a collection of gasps and groans from the audience. Schumacher — who took over Hadid’s firm following her death last year and is by no means the first architect to voice displeasure with the design — offered the opinion unsolicited, saying it was the biggest recent disappointment among projects recently delivered in New York City. (Hadid had offered up concept designs for four towers at the World Trade Center site.)

The remark was the only moment of tension during Friday’s panel, which was part of a real estate summit entitled “City of Tomorrow” held by Hundred Stories and the 92nd Street Y. Most of the discussion was cordial and complimentary, featuring Schumacher, Duffy, Liz Diller and Christopher Sharples. They discussed how they approach design and how they view their role in changing the city.

Diller, whose firm co-designed the High Line and 15 Hudson Yards, said that she at first didn’t care what people thought of her work — until she worked on the Blur Building in Switzerland. She said it was “a wakeup call” to how differently audiences can react to designs. She now cares about her audience but doesn’t exactly cater to it.

“We’re not thinking, ‘is everyone going to love it?’ We actually want to piss people off sometimes. We want to sometimes make people uncomfortable. But we are always thinking about a dynamic audience,” she said. “It’s impossible to just have blinders on and do something that is just for ego.”

She added that despite intention, designs can have unexpected consequences. Architects, therefore, have to think about their projects in a larger context than just “a building in time.”

“Sometime you’re going to contribute to the death of something or the rebirth of something,” she said.

When the discussion turned to public space, Sharples, one the founding principals at SHoP, noted his firm’s work on Pier 17 at the South Street Seaport with development firm Howard Hughes Corporation. He said private development can have a big impact on creating parks and public squares for residents.

“One of the things that we made clear when we started working with Howard Hughes was it can’t just be for tourists. It’s gotta be for New Yorkers, and it just can’t be for happy hour,” he said.

Duffy suggested that private developers should consider including public space on higher levels of their properties, rather than just the ground floor. He added that as more skyscrapers cast shadows on buildings’ lower levels, public space would be more valuable at higher elevations.

“We have things like observation decks and the like, but there’s no truly public space supported by buildings up in the air,” he said. “That could be a radical idea.”