Sydney  - Danish architect Joern Utzon was a creative genius who gave Australia and the world a great gift when he designed the Sydney Opera House, the custodian of the much-loved waterfront building said Sunday.

Utzon died in his sleep in Denmark on Saturday, aged 90.

Opera House Trust chairman Kim Williams said the lights that pick out the famous sails would be extinguished for an hour on Sunday night as a mark of respect. On Monday, the flags on the nearby Sydney Harbour Bridge were to be lowered to half-mast.

"It has become the most globally recognized symbol of our country," Williams said.