This was The Netherlands until 1932.
In the middle there was a rough inland sea (the Southern Sea), witch was directly connected with the North Sea
and what caused from time to time a lot of problems.
After a flood in 1916 we decided that the Zuiderzee would be enclosed and reclaimed: The Zuiderzee Works started.
The man in charge was the engineer Mr. Lely.
Between 1927 and 1932 we build a ‘closure dike’ running from the North Holland province to the Friesland province,
over a length of 32 kilometers (20 mi)
and a width of 90 meters (300 ft),
at an initial height of 7.25 meter.
That made the rough former Southern Sea into a calm and quiet lake. It closed off the sea completely.
After damming off the sea, the next step involved creating new land, known as polders.
This was achieved by damming off portions of the IJsselmeer, and then pumping all the water out.
We started with the Noordoostpolder (with capital Emmeloord).
We build a dike all around and pumped the water out of this area.
This new land included the former islands of Urk and Schokland.
Building the dike took us about four years (1936 – 1940) , pumping took about three years. (1940 – 1942)
After this, other parts were reclaimed:
the Southeastern part in 1957 (Lelystad)
and the Southwestern part in 1968.(Almere).