This list of tallest bridges includes bridges with a structural height of at least 200 metres (660 ft). The structural height of a bridge is the maximum vertical distance from the uppermost part of a bridge, such as the top of a bridge tower, to the lowermost exposed part of the bridge, where its piers, towers, or mast pylons emerge from the surface of the ground or water. Structural height is different from deck height, which measures the maximum vertical distance between the bridge deck (the road bed of a bridge) and the ground or water surface beneath the bridge span. A separate list of highest bridges ranks bridges by deck height.