@danryckert: a simplified explanation of how suspension bridges work (disclaimer: I am not a structural engineer): all pieces of a structure can either be in compression, where the stress is squeezing the ends together; or in tension, where the stress is pulling the ends apart. traditional structural materials like wood and metal are strong under both compression and tension, but they're heavy. metal cables, which are the load-bearing parts of a suspension bridge, are very light, but they also only work in tension; if you push on the ends of a metal cable, it's like pushing on the ends of a very large string.(source: http://www.wsdot.wa.gov/TNBhistory/Machine/machine1.htm)the trick of suspension bridges is to anchor a long main cable to the ground on either side of the bridge, string up the main cable above the bridge deck with towers, and then attach suspender cables between the main cable and the bridge deck. the weight of the bridge deck pulls on the suspender cables; the suspender cables pull on the main cable; and the main cable pulls inward on the anchorages at either end of the bridge.this way, the whole bridge is in tension -- and can be made out of light cable -- except for the towers the cable dangles from, which only need to support part of the weight. the rest of the weight is routed harmlessly to the anchorages on either end of the bridge, which can be made as big and heavy as you want because they're in solid ground.