In the 1930's they first built a dike that split the Waddenzee (part of the North Sea) and the Ijselmeer. Then a second dike in the 1970's that split the Ijselmeer and the Markermeer which borders Amsterdam.
Good quiz, forgot Monaco when time ran out. For a sprint quiz try my 60 sec Capital Quiz on ........ http://www.jetpunk.com/user-quizzes/120558/mals-1-minute-20-easiest-no-thinking-capitals-quiz
The quiz doesn't ask for capitals of European countries, only for capitals in Europe. So by that logic, Istanbul would qualify. If it was a capital, of course.
Monte Carlo is the largest quartier of Monaco, but Monaco is a City State, like Singapore or Vatican. To say Monte Carlo is the capital of Monaco is akin to Manhattan being the capital of NYC or Sandton the capital of Johannesburg. It's just not the case.
(I know this was a joke, just wanted to share that though.)
a caveat telling us where to meausure from wouldn't be too bad. i think i've seen rome count as a capital by the sea on another jp-quiz