Over the last decade Jaume Plensa has become one of the world’s most celebrated public artists, best known for monumental figurative sculptures that can be seen from Calgary to Dubai. But ask this Barcelona native how he creates his work, which seems to involve feats of technology, and he prefers to talk about dreams and poetry.

“Shakespeare is the best definition of sculpture,” he might say, quoting the “sleep no more” soliloquy from Macbeth. “You are working always with physical elements. You are always touching, touching. But you can’t describe it.”

Clearly, though, more than poetry has gone into “Echo,” his 13.5-meterhigh sculpture of a girl’s head that was raised in Madison Square Park in Manhattan in May. The work is made from an amalgam of polyester resin, white pigment and marble dust, and its glittering neck rises straight from the grass.

Mr. Plensa’s inspiration for “Echo ” was the nymph of Greek myth, condemned by Zeus to repeat the words of others. He wants it to jolt viewers into an awareness of their own voices.

“Many times we talk and talk,” he said, “but we are not sure if we are talking with our own words or repeating just messages that are in the air. ”

More of Mr. Plensa’s work is on display at Galerie Lelong in New York’s Chelsea neighborhood through June 18. Toronto has invited him to propose a public artwork, and he recently traveled to Chichester Cathedral in England, where he is creating a sculpture for the nave. His largest exhibition to date is at the Yorkshire Sculpture Park in Wakefield, England, through September 25.

“Plensa is a very interesting artist because he’s firmly rooted in the conceptual camp,” said Peter Murray, the executive director of the Yorkshire park, “but the making of the works is also very important.”

Early in his career, when Mr. Plensa began showing in Europe, he was known for working with cast iron, the medium of his first public sculpture, “Born” (1992), which put a chest and cannonballs on a Barcelona street. Later, he incorporated light and sound, as in “Love Sounds” (1998), a group of light-filled alabaster chambers that throb with the recorded sounds of his own body.

But for years he had dreamed of an “art totale,” he said, that would meld the disciplines of photography and sculpture. That finally happened in 2004, with “Crown Fountain” at Millennium Park in Chicago.

Two 15-meter-high glass towers, linked by a pool of water, play giant video portraits of a thousand Chicago residents, rotating at random.

Every few minutes each portrait purses its lips and spouts a jet of water, metamorphosing into a high-tech gargoyle.

“Crown Fountain” catapulted Mr. Plensa to renown and won the attention of the curator Brooke Kamin Rapaport, a member of the committee that advises the Madison Square Conservancy’s art program. “When we think of great modern and contemporary public art, usually we think of work that uses an abstract visual language,” she said. “But Plensa is using an everyday regular person as his source.”

Mr. Plensa ‘s first idea for the Madison Square Park project was a cluster of mammoth leaves . It was accepted, but when Debbie Landau, the director of the conservancy, visited Mr. Plensa’s studio last May to talk logistics, to her amazement, Mr. Plensa said, “I have a surprise for you.” He presented her with the model maquette for “Echo.”

Mr. Plensa began “Echo” as he does many of his heads: first making 3-D digital photographs of his subject - in this case the 9-year-old daughter of a man who runs a Chinese restaurant near his studio. Using computer modeling he alter s details so that the image “loses the journalistic sense of portrait to become an icon.” An industrial prototyping machine generates a plastic-foam scale model, which he recarves by hand.

This particular head was cast in 15 pieces in Spain and assembled
over a steel scaffolding on site with visible joins.

“When Jaume came up with ‘Echo,’ we had a lot of technical questions,” Ms. Landau said. “He would say, ‘We’ll figure that out later.’ He really did help us focus just on the work and not let details get in the way of making it happen.”

Mr. Plensa, hearing this, smiled. “Technique can be a problem if you think about it beforehand,” he said. “You just dream. Then you find a solution.”