High Quality Content by WIKIPEDIA articles! A pier is a raised structure, including bridge and building supports and walkways, over water, typically supported by widely spread piles or pillars. The lighter structure of a pier allows tides and currents to flow almost unhindered, whereas the more solid foundations of a quay or the closely spaced piles of a wharf can act as a breakwater, and are consequently more liable to silting. Piers can range in size and complexity from a simple lightweight wooden structure to major structures extended over a mile out to sea. In American English, pier may be synonymous with dock.