The Dutch and their ancestors have been working to hold back and reclaim land from the North Sea for over 2000 years. Over 2000 years ago, the Frisians who first settled the Netherlands began to build terpen, the first dikes to hold back the water.
In 1287 the terpen and dikes that held back the North Sea failed, and water flooded the country. A new bay, called Zuiderzee (South Sea) was created over former farmland. For the next few centuries, the Dutch worked to slowly push back the water of the Zuiderzee, building dikes and creating polders (the term used to described any piece of land reclaimed from water). Once dikes are built, canals and pumps are used to drain the land and to keep it dry. From the 1200s, windmills had been used to pump excess water off the fertile soil; today most of the windmills have been replaced with electricity- and diesel-driven pumps.
Then, storms and floods of 1916 provided the impetus for the Dutch to start a major project to reclaim the Zuiderzee. From 1927 to 1932, a 30.5 km (19 mile) long dike called Afsluitdijk (the Closing Dike) was built, turning the Zuiderzee into the IJsselmeer, a freshwater lake. (Much of the Netherlands is essentially a delta for the Rhine and other rivers.)
Further protective dikes and works were built, reclaiming the land of the IJsselmeer. The new land led to the creation of a the new province of Flevoland from what had been sea and water for centuries. The collective North Sea Protective Works is one of the Seven Wonders of the Modern World, according to the American Society of Civil Engineers.
Today, approximately 27 percent of the Netherlands is actually below sea level. This area is home to over 60 percent of the country's population of 15.8 million people. The Netherlands, which is approximately the size of the U.S. states Connecticut and Massachusetts combined, has an approximate average elevation of 11 meters (36 feet). The Netherlands ties Lemmefjord, Denmark for claim to the lowest point in Western Europe - Prince Alexander Polder lies at 23 feet (7 meters) below sea level.