Hiram M. Chittenden locks and spillway on the Lake Washington Ship Canal, Seattle, Washington state. The Ship Canal connects Lake Washington to Puget Sound via Lake Union, right thru Seattle. The locks, administered by the US Army(!) Corps of Engineers, deal with the difference in water level between the Sound and the lake. They're on the far (north) side of the spillway.
The Canal was built in 1916, lowering the level of Lake Washington some 9 ft. The lake used to drain out to the south to the Duwamish River, but now its only outlet is thru the Canal. There's no _way_ the project would pass environmental muster these days! ;) Because the Canal is now also the sole outlet for the lake, this set of spillway gates helps regulate water flow. The locks are also said to be unusual in that they're right at the boundary between fresh and salt water. The water in the foreground is Puget Sound.