The Afsluitdijk (Enclosing Dike) which closes off the IJsselmeer, 30km/18.5mi long by 90m/100yd across, links the provinces of Noord-Holland and Friesland. Built between 1927 and 1932, it converted the Zuiderzee into an inland lake, now known as the IJsselmeer. The Zuiderzee itself was an inland lake until Roman times; but during the early Middle Ages the level of the North Sea rose and gigantic storm tides broke through the land and made the Zuiderzee an inlet of the sea. Thereafter the government and people of the Netherlands wrestled with the problem of recovering the land drowned by the sea; but it was not until the 19th century that the technological resources for carrying through such a project became available. After severe food shortages in the Netherlands during the First World War and further heavy damage caused by a storm tide in 1916 the government approved a plan devised by a water engineer named Cornelis Lely, the object of which was twofold - to reclaim land for agriculture and to prevent further penetration by the sea. The construction of the Afsluitdijk had the effect of reducing the length of dikes in the IJsselmeer area by some 300km/185mi.At the near (southwestern) end of the Afsluitdijk is a group of sluices, the Stevinsluizen, which control the water level in the IJsselmeer. On the seaward side of the dike are a number of harbor basins enclosed by stone walls.
An excellent highway (A 7) runs northwest from Den Oever in Noord-Holland on the inland side of the Afsluitdijk dike, below the crown. To the right there are extensive views of the IJsselmeer; the view of the Waddenzee to the left is blocked off by the grass-covered crown of the dike. In 6.5km/4mi, on right, is a monument marking the point where the dike was finally closed on May 28, 1932. Here there are parking loting, an outlook tower with a small restaurant and a footbridge over the expressway; from the viewing platform there is a far-ranging prospect over the sea. Beyond this point is Breezandijk, an artificial island with a small harbor which was the starting-point for the construction of the dike. 11km/7mi farther on is another large group of sluices, the Lorenzsluizen; to the right is a parking lot, and beyond this, on the left, a restaurant. From here it is 4km/2.5mi to the end of the dike (gas station), on the west coast of the province of Friesland.