In a provincial parc domain near Leuven, Belgium you can find this nice example of a shelter with a green roof. It has been designed by Brick, an architect office from Antwerp specialised in ecological design.
Just decided: from February 2011 on in the city of Antwerp, Belgium, all flat roofs, new or renovated (with building permission) will have to be green roofs. A good way to buffer rain water and to reduce the urban heat island effect.