The visionary Danish architect who designed the Sydney Opera House has died.

Joern Utzon, 90, who won a competition to design the Opera House in 1956, died of a heart attack early on Saturday in Copenhagen.

The Australian Prime Minister Kevin Rudd led tributes to the architect, saying his legacy included one of the world's most "spectacular and inspiring buildings."

Mr Utzon began drawing up plans for the Opera House with its iconic sails in 1957. But he quit the project in 1966, seven years before it was finished, after a battle over its cost and his grand vision led to a bitter falling out with the New South Wales government.

Devastated at the collapse of his dream, and by insults to his masterpiece which included descriptions such as “albino turtles mating” and “nuns packing a scrum,” he left Australia, never to return.

He never did see the finished building, which was completed by Government architects who redesigned his interiors so they had no bearing to his original designs. To this day, the Opera House is criticised for the poor acoustics in some of its most important theatres.

He was haunted for the rest of his life by the disastrous end of his involvement with the building that has become one of the world's most recognised pieces of architecture.

But he always insisted he was not bitter. "It's part of education - I can't be bitter about anything in life,'' he said in 1998.

The rift between Mr Utzon and Australia was healed, eventually. Although he turned down any invitations to return to Australia, he did, latterly, collaborate at a distance on the most recent plans to alleviate acoustics problems.

In 2003, he was awarded the Pritzker Architecture Prize, the most prestigious in architecture, for the sculptural building that the jury singled out as among the most iconic buildings of the 20th century.

He has also been awarded an honorary doctorate by the University of Sydney for his work on the Opera House, as well as receiving the Order of Australia and the keys to the City of Sydney.

Last year his redemption was total when his once reviled design was added to the United Nations list of the world’s natural and cultural treasures.

Today, the chairman of the Sydney Opera House Trust, Kim Williams, paid tribute to the architect. The lights on the Opera House will be dimmed tonight in his honour, he said.

"Joern Utzon was an architectural and creative genius who gave Australia and the world a great gift,'' Mr Williams said.

"Sydney Opera House is core to our national cultural identity and a source of great pride to all Australians. It has become the most globally recognised symbol of our country.''

Born April 9, 1918, in the Danish capital of Copenhagen, Utzon graduated from the city's Academy of Arts in 1942.

His earliest buildings were private homes and many were surprised when he won the competition to design the Opera House.

However he went on to become recognised as one of the Twentieth Century's most brilliant architects designing, amongst other iconic buildings, the National Assembly building in Kuwait City. Constructed between 1971 and 1983, the parliament building is made of concrete and its shape evokes a series of large tents, traditional meeting places for Kuwait's Bedouin nomads.

Amongst other awards during his lifetime are the Sonning Prize for contributing to European culture, and the Order of Australia.

Mr Otzon is survived by his wife Lis and sons Kim and Jan, with whom he collaborated on a number of projects in Copenhagen.

Tomorrow, the Australian flags on top of the Sydney Harbour Bridge will fly at half mast in his honour.

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