A troubled project from the start, the cost of the Sydney Opera House ballooned from an estimated $7.2 million in 1957 to $120 million upon completion in 1973. The original design by Joern Utzon was determined to be unbuildable. Despite the difficulties, this internationally recognized monument to perseverance and innovation still graces Sydney's harbor.

Take a look at other significant projects over the past fifty years in which concrete and industry innovations played a major role.