Recently the dyke stone benchmark (called the “Huddestone”) was restored. During the demolition of “De Nieuwe Brugsluis” in 1955 it was lost, but it was rediscovered during the construction of the metro in 2014. The image below show this historical marble stone both before its loss and after its rediscovery.
Read the article in the district newspaper (Dutch only) (Stadsdeelkrant.pdf)
During Thursday`s night on 6th of december 2013 the sea level rose to 3,99 meters (about 13,09 feet) above NAP. It was the highest level measured since the disaster of 1953 , when the water reached a level of 4,55 meters (14,93 feet) above NAP, the dykes breached in many places and more than 1800 people drowned.
On 18th of May 2013, it was 25 years ago that the NAP monument was opened by the then Minister of Transport, Public Works and Water management, Mrs Smit Kroes.
The NAP-project was designed and realized by Louis van Gasteren and Kees van der Veer. The project was offered by the NAP-foundation on the occasion of the opening of the new Amsterdam City Hall (De Stopera). After a renovation and expansion with an exhibition, the NAP-monument was re-opened on the 12th of Oktober 2010 by the then Crown Prince Willem-Alexander.