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

Another big obstacle came with the shape of the building. How can you subdivide a triangle (just 1.8 m (6 ft) wide 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 loved by New Yorkers,” Thomas Brodsky, a partner at the Brodsky Organization, told the BBC.

“The layouts, proportions and views really came directly from the architecture and not from how we usually start planning a building from scratch.”

Originally designed to evoke a classical Greek column, the structure’s limestone, brick and terracotta exterior features ornamentation including lion heads, crowns, eagles and faces.

Beyer Blinder Belle, lead developer of the building’s exterior, hired a specialty fabricator in California to replicate and restore thousands of terra cotta pieces from the façade, reinstalling each one by hand.

The building’s windows, in total more than 1,000, also had to be replaced: they dated from the 1970s, were too heavy, difficult to open and were not energy efficient.

The new ones are thick enough to block out noise from surrounding streets, offering a quietness in the units that is uncharacteristic of New York City apartments.