When New York design firm Studio Sofield was hired to reimagine the building’s interior, it had to address the problem of the building’s previous life as an office space, co-founder William Sofield said.

Another big hurdle came with the building’s shape. How do you subdivide a triangle – just 1.8m (6ft) across at its narrowest point – into luxury apartments worthy of a multimillion-dollar price tag?

But the triangle itself – along with its history, architectural ingenuity, and novelty – is exactly the point.

“It wasn’t about changing anything that makes the building so special and beloved to New Yorkers,” Thomas Brodsky, partner at the Brodsky Organization, told the BBC.

“The layouts and the proportions and views really came directly from the architecture rather than from how we generally would start planning a building from the ground up.”

Originally designed to evoke a classic Greek column, the structure’s limestone, brick and terra-cotta exterior features ornamentation including lion heads, wreaths, eagles, and faces.

Beyer Blinder Belle, lead developer on the building’s exterior, enlisted a speciality manufacturer in California to replicate and restore thousands of terra-cotta pieces from the facade, reinstalling each by hand.

The building’s windows, totalling over 1,000, also needed to be replaced – dating back to the 1970s, they were too heavy, hard to open, and not energy efficient.

The new ones are thick enough to block the bustling noise of surrounding streets, offering silence in units that’s uncharacteristic of New York City apartments.