One of the first modern icons was the Sydney Opera House, designed by Jørn Utzon in 1957-73. Upon completion, it was internationally recognized as an Australian symbol. But a symbol of what? According to Charles Jencks, the author of Iconic Building, the white forms can be read as sails, waves, seashells, or copulating turtles. None of which has anything to do with music, but in some vague way seems just right for Sydney's harbor. Jencks defines iconic buildings as delicate balancing acts between what he calls explicit signs and implicit symbols, that is, between an unusual, memorable form and the images it conjures up. He emphasizes that in an increasingly heterogeneous world, multiple and sometimes even enigmatic meanings are precisely what turn a building into a popular icon.