As much as 50% of its land lie less than one meter above sea level.
With two thirds of its area vulnerable to flooding, flood control is an important issue for the Netherlands.
Among the various barriers constructed two stand out: one is Maeslantkering and the other is Oosterscheldekering.
The Maeslantkering acts as a final line of defense for Rotterdam against high levels of incoming seawater.
It is one of largest moving structures on Earth, and the most impressive project of Delta Works.
It is the only storm surge barrier in the world with such large moveable parts.
They are then flooded and the additional weight makes them sink and turns them into a massive barrier.
The Maeslantkering is expected to be closed once every ten years due to a storm surge.
Since construction was finished in 1997, the doors were closed only once in November 2007.
These doors are normally open, but can be closed under adverse weather conditions.
The dam is designed to last more than 200 years.
