A 1960s design competition called on architects from around the world to submit ideas for what would be the new Sydney Opera House.
The iconic building is celebrating 50 years since opening in 1973.
But for Jan Utzon, the son of Danish architect Jørn Utzon, the building's history really started 66 years ago when his father won the competition.
Just days after their youngest son was born, Jan's mother and father received the life-changing call which would see their family move around the globe.
Daughter Lin Utzon described the euphoria among her family and her parent's friends in Denmark, saying people were "absolutely ecstatic" for her father.
"Imagine as a young architect to look into a possible future asking him much more than he could have imagined," she said.
"(His design) could really fly and it was brilliant."
Celebrating the 50th birthday of the Opera House, Jan and Lin travelled from Denmark to give a special lecture on Tuesday reflecting on their father's legacy and their memories of the design.
Audience members included people who worked on the construction of the building in the 1960s and 1970s, workers involved in the renovations in the late 1990s and early 2000s and those who worked on the most recent renewal project.
Multiple Utzon descendants including children, grandchildren and family members also attended.
Jan said his father drew on architectural inspiration from his global travels to inform his design.
"My father travelled to and from Australia multiple times often via Japan, China, India, Iran, where was inspired by all these different types of art," he said.
"He was just pulling on inspiration all the time, he did not copy things but he was inspired by their art, many of which is used in this project here."
Australian architect Richard Johnson, a university student while the building was under construction, said he and other budding architects would visit the site often.
"Intuitively we all felt there was something magical emerging from this place," he said.
"It's something that stays with you, because it is magic."
Initially the project was expected to cost Stg 4 million (A$7.66 million), but the final figure was closer to Stg 51 million (A$97.64 million).
Lin said the cost, and criticism that came with it, wasn't really discussed by her family.
"(Midnight Oil frontman) Peter Garret produced a record where you have an image of Sydney, which has disappeared after a volcanic eruption, the only thing that's left is the Opera House," she said.
"It feels as if the Opera House was found and was excavated, it would be the most brilliant, beautiful reminder of what architecture can be."
