The Sydney Opera House is a masterpiece of 20th-century architecture designed by Danish architect Jørn Utzon. Opened in 1973, it is famous for its gleaming white 'shells' or 'sails.' These shells are actually composed of precast concrete panels covered in over one million Swedish ceramic tiles. The design was so complex that it required the development of new computers and structural engineering techniques to solve the geometry of the roof. Interestingly, the shells are all segments of the same sphere, a solution Utzon found while peeling an orange. Despite a construction process that went significantly over budget and took 14 years longer than planned, it is now Australia's most recognizable landmark and a UNESCO World Heritage site. It hosts more than 1,500 performances annually, attended by some 1.2 million people.