The Netherlands used to flood a lot. Rather than just grow gills and be done with the matter, the Dutch blew a bunch of cash on a massive set of levees, then added this monumental storm surge protector up front.
The $US3.3 billion dollar Oosterscheldekering is the largest of the Netherland's 13 Delta Works dams. It's goal: to reduce flooding in the Southern part of the country to once every 10,000 years. The rest of the nation will get it once every 4,000. America will get it, RIGHT ABOUT NOW.
It spans 9km across the Oosterschelde estuary and was by far the the most difficult and expensive portion of the Delta Works project. Essentially a massive floodate, it's comprised of 65 concrete pillars—weighing 18000 tons apiece—that support 62 steel doors. Each door is 42 meters wide and takes a full hour to swing closed — just enough time for a smoke and a pancake. (smoke whatever you like—this is the Netherlands, after all.)
The Oosterscheldekering was originally envisioned and (partially) built as a solid dam, which would have turned the Oosterschelde into a freshwater lake. However, after numerous environmental protests and much political wrangling, designers added the gates to allow salt water to cycle through with the tides. These gates only close when sea levels rise more than 3 meters, something that's happened about 24 times since its completion in 1986. Never hurts to be prepared!