Due to its loca­tion in the delta of the riv­er Rhine, Rot­ter­dam is often referred to as Delta Metrop­o­lis. As impres­sive as that may sound, it also entails some chal­lenges. What to do with increas­ing pre­cip­i­ta­tion in a city that lies large­ly below sea lev­el, and where water comes from all direc­tions: from the sea, the riv­er, the ground and the sky? The most pop­u­lar key­word at the moment is meer­voudig ruimtege­bruik, i.e. mul­ti­cod­ing. This approach results in projects such as a pub­lic square that also serves as rain­wa­ter reten­tion facil­i­ty, or a veg­etable patch on the roof of an office block. For­mer­ly neglect­ed office dis­trict Zomer­hofk­warti­er has even been declared a test field for rain­wa­ter reten­tion projects.