Holland
Nederland is called this way because parts of Nederland are lower than the sea level.
everything blue is below sealevel!
The deltaplan was constructed because there was a fload in the coast of Sealand .
.
There were build dikes and dunes around the coast area to.
The dikes were build and the dunes are formed by nature.
With a lock we can control the water level
dune
dike
dike
The Nederlands is a little upper orange country in the left on this map.