To see the one and only real Normal Amsterdam Level (NAP), you have to go to the passageway between the Town Hall and the Music Theater on Waterlooplein square. The NAP has become the standard for measuring water levels in virtually every European country. 

Flood disaster
The NAP post comes right up through the building from the second sand layer. On this post is the bronze NAP gauge. From the floor, three glass water columns also rise up. The water in two of these columns show the up-to-date high tide and low tide levels of the sea at Vlissingen (Flushing) and IJmuiden. The water level in the third column is frightening. The water surges up to almost five meters above your head. This is the level the seawater reached during the flood disaster in the province of Zeeland in 1953. The wall of the passageway shows a cross-section of Holland between the IJsselmeer lake and the North Sea. It gives details on water management in Holland. An explanation in six languages is available on the spot. 

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