Everyone was dressed in black, and all eyes were on two Americans who had never met before. Martha Schwartz, the colourful landscape architect and artist, had driven out with her clients from the Dublin Docklands Development Authority (DDDA) to a country house near Dublin airport to unveil her radical design for the capital’s most spectacular new plaza, Grand Canal Square.

The developers and architects for the buildings that will form the edges of the new square were there to meet her, eager to see what she had come up with. In the cultish world of high architecture, where people wear black and buildings come in shades of grey, Schwartz’s exciting designs stand out like psychedelic peacocks.

One thought rippled through the Devey Group’s boardroom that afternoon early last September: how would Daniel Libeskind, the world-famous master planner of ground zero and architect of Devey’s iconic, crystalline performing-arts centre for Grand Canal Square, react? Schwartz cracked a joke; the ice was broken. Libeskind responded with a joke of his own.

Soon he was asking to borrow an image of her proposal to include in the public lecture he would give in Dublin that evening. “It’s great for the project, it’s great for the team,” he told his audience later. “We’re going to work together. She’s a creative artist. It will be a spectacular destination. That’s the big living room.

“It creates a context for the buildings. The great schism of the 20th century was when master planning became disconnected from architecture. They weren’t two different fields in the past. That’s what’s at stake here.”

Schwartz was coming late to the team, years after Grand Canal Square had been built in the immediate aftermath of 9/11. Confidence in the property market had been dented by the attack on the twin towers in 2001 and DDDA urgently needed to send out a message to would-be developers of the bleak former gasworks site on Grand Canal Dock.

So they built the square — little more than a paved-over underground car park — without a context. The ploy was successful, initially at least. The market bought in. There would be offices, shops, a luxury hotel and a 2,000-seater theatre. The architecture would be spectacular, if radically different on each of the square’s three enclosed sides.

At a review meeting with the developers and their architectural teams in Libeskind’s New York studio in December 2004, however, the shortcomings of Grand Canal Square suddenly became clear to everybody: DDDA, the developers and their architects — Libeskind, Manuel Aires Mateus from Lisbon and Duffy Mitchell O’Donoghue from Dublin.

It was too introspective. Conceived in a vacuum and set below the surrounding street and quay level, it didn’t relate to the buildings now planned for its edges. The car park ramps cut the hotel off from the open surface.

The space was also too neutral for Libeskind’s guiding concept of stages: the stage of the theatre; the stage of the multi-storey theatre lobby, illuminated at night, with its projecting balconies and incised gardens; and the square itself as a stage for civic gathering.

They would have to reconfigure the space to relate to the water on the square’s open side: the vast, non-tidal dock. The focus would shift from the buildings around the edges to the public space in the middle. A joined-up approach was needed — and quickly.

The DDDA went looking for a saviour and early last year they found Schwartz, a Harvard professor with studios in Boston and London, who has over the past 25 years almost single-handedly redefined the notion of landscape architecture by bringing an entirely new design language to a traditionally horticulture-oriented discipline.

Eschewing the conventional notions of landscape, her mix of bold formalism, vibrant colours, artificial materials and unexpected plants has breathed life into a moribund profession.