The Seine Basin is a vast territory stretching from Burgundy to Normandy, encompassing more than 18 million inhabitants. The multiple tributaries of the Seine form a spectacular array that traverses, irrigates, and connects rural areas, metropolises, valleys, and plains. This is the result of nature's slow work over centuries, shaping the landscapes of our daily lives.

The Seine Basin is a living environment for humans as well as other animals and plants, hosting a diversity of life. Its benefits for ecological and evolutionary processes are a resource to protect and adapt human societies in the face of global changes.

Faced with the simultaneous threat of water scarcity and the risk of flooding due to climate change, Les Ateliers de Cergy proposes that we take a fresh look at the Seine Basin. As the primary condition for life, water is at the heart of the relationship between geography, landscape, living organisms and minerals. Building on the hydrographic network, the symbolism of water and the narrative power of gardens, how can this Great Sequanian Garden be created?

The aim of the workshop is therefore to contribute to the invention of this Great Sequanian Garden, to invent the narratives of desirable, supportive and resilient territories for the inhabitants of this vast watershed. Following the river from its source to its estuary, this 43rd session will focus on the Upper Seine Valley–Seine Amont section.

The workshop main challenges

Foster a shared water culture : What can be done to reconcile uses, reduce conflicts and conserve water resources?

Imagine elements of a territorial narrative : How can the imagination be stimulated through storytelling mechanisms? What can they be they be based on? How can they be embodied and made collective?

Mobilize knowledge for territorial development : To encourage the application of proven knowledge, what strategies are needed to integrate this knowledge into territorial projects?

Raise awareness of hydrosolidarity : How can interdependence be translated into new forms of action and governance?As part of the 43rd session of the International Urban Planning Workshops, the Ateliers de Cergy propose to place water at the heart of territories. *

The Ateliers thus invite the territories of the Seine Basin and various water stakeholders to join this reflection, culminating in an international urban planning workshop. Twenty young professionals and students from around the world will work in teams for 20 days in September 2025 to collaboratively and creatively propose bold ideas to outline a grand "Seine Garden."