Watch your a(l)titude...

Holland is a country that fights (and has always fought) against water. Without dikes or dunes, Holland would look like this (blue means "under water"):

Delft is roughly the red dot. According to a website where I could fill in my house postcode, I live at +1.1 m compared to the reference level... I was quite pleased, untill I discovered a detailled map of the water-level of Delft (yellow above water):

... it seems that only the buildings are at a "positive" height! (the deep blue around Delft is at a level of circa -5 m...). Moreover, if dunes and dikes would not exist, even the first picture is not true: Holland would erode since it is mostly formed by sediment (cohesive or not). The first rocky (solid) ground is found close to german border.