you can go to "The Slufter" ! it a pretty place with windmills, a protected area for birds and other rare animals, at the other side of the street there is a huge place where compagnies can dumps all sorts of garbage and perhaps even barrels of toxic materials !!
but, as you asked, its flat... otherwise you can go to the "Car less beach", it pretty shallow water and after parking it takes a 10 minute walk..
Nou, mooier kan ik het niet laten klinken in het engels, die zullen we daar wel nooit zien !!!