|Normaal Amsterdams Peil (NAP) or Amsterdam Ordnance Datum is a vertical datum in use in large parts of Western Europe. |
Originally created for use in The Netherlands, it was adopted by Germany in 1879 under the name Normal Null, and in 1955 by other European countries.
In the Amsterdam City Hall you can see the N.A.P. A bronze bolt shows the exact height of the N.A.P.