Hong Kong Airport was built on reclaimed land from the sea to address challenges with the existing airport. A new island was created by joining two rocky islands and moving over 600 million tons of rock and sand. The massive construction project involved building three runways, the world's largest airport terminal, and infrastructure like a double-decker suspension bridge and an underwater tunnel. The new airport opened in 1998 and became the world's busiest, facilitating Hong Kong's international trade.