Jorn Utzon, a Danish architect who designed one of the world's most recognizable buildings, the Sydney Opera House, but never saw it finished, died in Copenhagen on Saturday. He was 90.

He died of heart failure in his sleep, according to his son Kim.

Floodlights that illuminate the Opera House were dimmed for one hour Sunday night to mark Utzon's death, The Associated Press reported from Sydney, and the New South Wales government said flags on the city's other landmark, the Sydney Harbor Bridge, would be lowered to half-staff Monday.

Utzon left Australia amid controversy seven years before the Opera House was completed. He lived out most of his final decades on the Spanish island of Majorca while his gull-roofed building came to symbolize Australia, half a world away.

As a young architect Utzon worked for Gunnar Asplund in Sweden and Alvar Aalto in Finland before establishing his own practice in Copenhagen in 1950. In 1956, he read about the Sydney Opera House competition in a Swedish architecture magazine. He spent six months designing a building with sail-like roofs, their geometry, he said, derived from the sections of an orange. Utzon's plan was championed by Eero Saarinen, the Finnish architect who was one of the judges in the competition.