A bridge or bridge is a structure built across a canyon, valley, road, railroad, river, other waters, or other obstacles. It is an elevated structure that protrudes from the surface of the water or the ground and is used to connect the two sides of the bridgehead. The purpose of the bridge is to allow people, vehicles, trains or ships to pass through obstacles. The bridge can be crossed across the valley or the strait, or it can rise on the ground and cross the river or road below to make the traffic below unimpeded. The "bridge" was originally a tall tree (see arbor). Because it is tall enough, it can be long enough to be cut down on the river, and it can be connected to the two sides, that is, the wooden bridge. The space that the open and closed bridges pass to the big ship. A bridge is a large structure used to span obstacles. Specifically, it is used to cross traffic routes (such as roads, railways, waterways, etc.) or other facilities (such as pipes, cables, etc.) across natural obstacles (such as rivers, straits, canyons, etc.) or artificial obstacles (highways, railway lines). Structure.