Why this twist?

During the first phase, the drain locks were built. At low tide, these drain locks would allow the excess water from the Ijsselmeer (water from the Ijsselmeer and rain water) to be drained into the Waddenzee. Five groups of five drain locks are used in the Afsluitdijk, except that one of the drain locks was unable to be installed in the required location. The direction of the dike had to be adjusted to the north where it would have to cross the “Middelgronden” (“Middlegrounds”), a 12-metre deep channel. It was decided to cross this channel at the shallowest possible depth, which is the reason for the dip in the Afsluitdijk. In the end, three groups of drain locks were installed near Den Oever and two groups were placed at the Kornwerderzand. The 32-kilometre long Afsluitdijk was completed on 28th May, 1932.

Some facts and figures of the Afsluitdijk:
- The Afsluitdijk is 32 kilometres long
- 2.5 kilometres of dike is situated between Noord-Holland and Wieringen, and 30 kilometres of dike is situated between Wieringen and Friesland.
- At the water line, the Afsluitdijk is 90 metres wide and has a crown height of 6.80 to 7.50 metres over NAP.
- Each drain lock is 12 metres wide and 4 metres deep.
- Building the Afsluitdijk required 15 million cubic metres of boulder clay and 27 million cubic metres of sand; you can fill many sandpits with that!