European great cities are now facing four major challenges. The first one is about managing drinking water in urban areas (distribution, prices, access and supply). Water management has become the main tool to protect water extraction areas or manage the ground- and surface water in unpolluted areas out of the city. The second challenge concerns the sanitation of waste- and rainwater. The long-term goal implies separation storm water and rainwater more efficiently, without congesting municipal networks during rainy periods and modernizing the processes used to purify industrial and domestic waste water. The third challenge refers to water courses and small urban rivers. Cities now strive to reclaim rivers that were once buried, through reopening them. That goes along with a transformation of riverbanks to large public spaces by pushing back roads and economic activities. The last challenge deals with the urban resilience to flood risks as a new alternative to local flood risk management policies, which are still very much focused on standard and heavy flood protection (dykes, dams, etc.). The first two topics are about the “little water cycle” (water management from the collecting points to the treatment plants before returning to the natural environment). The last two issues relate to the big “natural” cycle of water. The following paper proposes a reflection on strategies by three of the biggest European metropolises in regards to their water management policies and their proceeding -via urban planning projects- to merge the two “water cycles”. The article is based on the result of international projects in which two of the authors have been involved in.