Sydney Harbour Bridge, Australia

Opened in 1932, the Sydney Harbour Bridge is the world's largest steel arch bridge, with an arch span of 503 meters and a total length of 1,149 meters. Known as "The Coathanger," it required 52,800 tonnes of steel and employed 1,400 workers during the Depression, costing £4.2 million—10% less than the Golden Gate Bridge's $35 million at #1. It carries eight lanes of traffic, two rail lines, a cycleway, and a footway, handling 200,000 vehicles daily, 30% more than the Millau Viaduct's 10,000 at #2. The arch rises 134 meters above the harbor, making it the fifth-longest spanning arch bridge on Earth. Its nine-year construction period was 33% faster than the Akashi Kaikyo Bridge's decade-long build at #4, cementing its role as a vital transport hub.