Afsluitdijk in the context of "Sluice"

Lelystad (Dutch pronunciation: [ˈleːlistɑt] ) is a Dutch municipality and the capital city of the province of Flevoland in the central Netherlands. The city, built on reclaimed land, was founded in 1967 and was named after Cornelis Lely, who engineered the Afsluitdijk that made the reclamation possible. Lelystad is situated approximately three metres (10 feet) below sea level.

Flevoland (Dutch pronunciation: [ˈfleːvoːlɑnt] ) is the twelfth and newest province of the Netherlands, established in 1986, when the southern and eastern Flevopolders, together with the Noordoostpolder, were merged into one provincial entity. It is in the centre of the country in the former Zuiderzee, which was turned into the freshwater IJsselmeer by the closure of the Afsluitdijk in 1932. Almost all of the land belonging to Flevoland was reclaimed in the 1950s and 1960s while splitting the Markermeer and bordering lakes from the IJsselmeer. As to dry land, it is the smallest province of the Netherlands at 1,410 km (540 sq mi), but not gross land as that includes much of the waters of the fresh water lakes (meres) mentioned.

The province had a population of about 445,000 as of January 2023 and consists of six municipalities. Its capital is Lelystad and its most populous city is Almere, which forms part of the Randstad and has grown to become the seventh largest city of the country. Flevoland is bordered in the extreme north by Friesland, in the northeast by Overijssel, and in the northwest by the lakes Markermeer and IJsselmeer. In the southeast, the province borders on Gelderland; in the southwest on Utrecht and North Holland. Outside urban areas, the land in Flevoland is predominantly used for agriculture.

The Markermeer (Dutch pronunciation: [ˌmɑrkərˈmeːr]) is a 700 km (270 sq mi) lake in the central Netherlands in between North Holland, Flevoland, and its smaller and larger neighbors, the IJmeer and IJsselmeer. A shallow lake at 3 to 5 m in depth, matching the reclaimed land to its west, north-west and east it is named after the small former island, now peninsula, of Marken on its west shore.

The Markermeer was not originally intended to remain a lake. It was formerly part of the Zuiderzee, a saltwater inlet of the North Sea, that was dammed off by the Afsluitdijk (Closure Dike) in 1932, turning the Zuiderzee into the freshwater IJsselmeer. The following years saw the reclamation of extensive tracts of land as large polders in an enormous project known as the Zuiderzee Works. One of these, the Markerwaard, was to occupy the area of the current Markermeer. Part of the construction of this polder was building the Houtribdijk, also called Markerwaarddijk, finished in 1976, which hydrologically splits the IJsselmeer in two, the southern section being the Markermeer.

Cornelis Lely (Dutch pronunciation: [kɔrˈneːlɪs ˈleːli]; 23 September 1854 – 22 January 1929) was a Dutch politician of the Liberal Union and civil engineer who was Minister of Water Management and Governor of Suriname. The designer of Afsluitdijk, the largest dam and causeway at its time of construction, in 1932, he oversaw the Zuiderzee Works as Minister, turning the Zuiderzee into a lake and making possible the conversion of a vast area of former seabed into dry land. His plan deeply transposed and influenced the current geography of the Netherlands. Lelystad, the capital of the province of Flevoland, is named after him.

The Wadden Sea (Dutch: Waddenzee [ˈʋɑdə(n)zeː] ; German: Wattenmeer [ˈvatn̩ˌmeːɐ̯] ; Low German: Wattensee or Waddenzee; Danish: Vadehavet; West Frisian: Waadsee; North Frisian: di Heef) is an intertidal zone in the southeastern part of the North Sea. It lies between the coast of northwestern continental Europe and the range of low-lying Frisian Islands, forming a shallow body of water with tidal flats and wetlands. It has high biological diversity and is an important area for both breeding and migrating birds. In 2009, the Dutch and German parts of the Wadden Sea were inscribed on UNESCO's World Heritage List and the Danish part was added in June 2014.

The Wadden Sea stretches from Den Helder, in the northwest of the Netherlands, past the great river estuaries of Germany to its northern boundary at Skallingen in Denmark along a total coastline of some 500 km (310 mi) and a total area of about 10,000 km (3,900 sq mi). Within the Netherlands, it is bounded from the IJsselmeer by the Afsluitdijk. Historically, the coastal regions were often subjected to large floods, resulting in thousands of deaths, including the Saint Marcellus' floods of 1219 and 1362, Burchardi flood of 1634 and Christmas Flood of 1717. Some of these also significantly changed the coastline. Numerous dikes and several causeways have been built, and as a result recent floods have resulted in few or no fatalities (even if some dikes rarely and locally have been overrun in recent history). This makes it among the most human-altered habitats on the planet.

The Zuiderzee or Zuider Zee (Dutch: [ˌzœydərˈzeː] ; old spelling Zuyderzee or Zuyder Zee), historically called Lake Almere and Lake Flevo, was a shallow bay of the North Sea in the northwest of the Netherlands. It extended about 100 km (62 mi) inland and at most 50 km (31 mi) wide, with an overall depth of about 4 to 5 m (13 to 16 ft) and a coastline of about 300 km (190 mi). It covered 5,000 km (1,900 sq mi). Its name is Dutch for "southern sea", indicating that the name originates in Friesland, to the north of the Zuiderzee (cf. North Sea).

It is generally acknowledged that the Zuiderzee existed from roughly 1170, following the devastating All Saints' Flood, until 1932, when the Afsluitdijk was completed. The majority of the Zuiderzee was closed off from the North Sea, leaving the mouth of the inlet to become part of the Wadden Sea. The salt water inlet changed into a fresh water lake now called the IJsselmeer (IJssel Lake) after the river that drains into it, and by means of drainage and polders, an area of some 1,500 km (580 sq mi) was reclaimed as land. This land eventually became the province of Flevoland. Part of the IJsselmeer was also divided into the Markermeer.

The IJssel (Dutch: [ˈɛisəl] ; Dutch Low Saxon: Iessel(t) [ˈisəl(t)]) is a Dutch distributary of the river Rhine that flows northward and ultimately discharges into the IJsselmeer (before the 1932 completion of the Afsluitdijk known as the Zuiderzee), a North Sea natural harbour. It more immediately flows into the east-south channel around the Flevopolder, Flevoland which is kept at 3 metres below sea level. This body of water is then pumped up into the IJsselmeer.

It is sometimes called the Gelderse IJssel (IPA: [ˌɣɛldərsə ˈʔɛisəl] ; "Gueldern IJssel") to distinguish it from the Hollandse IJssel. It is in the provinces of Gelderland and Overijssel, the latter of which was named after this river. The Romans knew the river as Isala. It flows from Westervoort, on the east side of the city of Arnhem.