The "Arch Bridge" is quite economical (cheap) to build. It can span a very deep chasm and maintain support throughout the span. The arch bridge is strong because no one point along the arch supports more mass than any other point - thus, the mass is spread out VERY evenly --> force spread out both downwards & outwards from the centre. Modern day arch bridges (they were used as far back as the Roman Empire!) use both steel and reinforced concrete as the basic materials. Arch bridges made of steel are constructed by joining curved beams of steel. The building process is interesting. Builders start adding the curved beams at either end of the span until they meet in the middle!
See a close-up of the arches of Confederation Bridge in Canada (although Confederation Bridge is really a "Beam" Bridge).
One of the most famous and widest steel arch bridges is the Sydney Harbour Bridge in Australia.