Behind this door is the expansion tank used to maintain the water pressure. The other door leads out onto the roof terrace. Imagine what the view would have been like from here towards the river Maas. Nowadays the Dijkzigt hospital is in the way, but in the early 1930s there was a panoramic view. The Boijmans van Beuningen Museum was being built, along with a park full of villas for wealthy local people, but apart from that it was all open space. During the Second World War, people took refuge here from the bombing, and Mrs Sonneveld reputedly took them cups of coffee. However, instead of using her best tea service, she had some old cups brought up from the cellar — you never knew what might happen to them. Rotterdam might have been in ruins, but Mrs Sonneveld got every one of her cups back unscathed. On the flat roof, apart from the simple, attractive little structure at the top of the stairs and the expansion tank, there's a cleverly designed windbreak. The two side screens can be turned so that people could sit in the sun but out of the wind.

The next commentary in the tour, number 18, is about the serving room. To get there, please go down one floor, to the first floor. The serving room is diagonally opposite the stairs.