Gwilen is the Breton name for the Vilaine, the longest river of the Armorican peninsula. Taking its source at the edge of Mayenne, it flows through Ille-et-Vilaine, crosses Rennes, continues its course through Morbihan, to go to throw itself in the heart of Mor Braz, between Pénestin and Muzillac. Mor-Bihan, literally little sea, designates the Gulf that inhabits it, this little sea punctuated, as the ancients say, by as many islands as there are days in a year; Mor-Braz is its big sister, a maritime expanse closed off to the southwest by the islands of Houat and Hoëdic, to the west by the Quiberon peninsula, to the north by the Rhuys peninsula, and to the east by Guérande, the land of the salt workers. This large sea, sheltered from the violence of the Atlantic Ocean and the swells of the open sea, is a protected space, a preserved ecosystem, an estuarine zone where fresh water mixes with salt water, a point of balance and transition. A fragile ecosystem, in balance between two worlds: the ocean and the continents. A fragile place welcoming nesting birds and migratory birds stopping over on their long journey, finding there a refuge and a rest. Avocets, Brent Geese, Shelducks, Eared Oystercatchers, Miquelon Duck, Red-throated Loon, Black Scoter and Greater Scaup live in the heart of the mudflats and salt meadows, between saltwort and Spartina meadows, cohabiting with otters and mink that have taken up residence there. This fragile balance was disturbed by man, who built a dam along the Vilaine River in order to create an important fresh water reserve supplying the equivalent of two departments with drinking water. A necessity to preserve its sedentary species. This infrastructure is a structure on the scale of the territory. A human construction which by its dimensions and especially its impact, is on the scale of natural phenomena: water flow and watersheds, topography, hydrology, geology, sedimentation. These scales are beyond us and are those of Nature. This Nature to which we belong, these ecosystems in which we live. Our constructions and infrastructures shape the landscape. The materials that we extract, transform, move and implement, are as many modifications of the "natural" aspect of the world, by the extraction that they require, real geological scars, as well as by the heap of inert materials that are our architectures and our infrastructures, transforming our environment to the point of recreating it from scratch in the heart of the cities, where Nature has its place only by anecdotes, like a tree planted under a tar. Is Nature what exists without Man? Are we parasites that derail the world? It seems to us that here again it is a question of balance. It is with great delicacy and attention to the territory that we must conceive our infrastructures, conscious of the imbalances that they can generate, conscious of the scale at which we are capable of thinking. It is not a question of questioning the validity of these dams, ports, bridges or roads, but of measuring the extent of our impact as humans. A tangible impact through these infrastructural examples that we live with and that we carelessly practice. It took two generations for the natural aspect of this estuary to be transformed, for its new morphology to become in the minds of men, its new naturalness. This relationship to time is fundamental. Our lightning passage on Earth is like the spark that Humanity represents for the Blue Planet. Jacques Ellul in "The Technological Bluff" wonderfully describes the progressive compacting of our time, its acceleration which is measured today at the speed of an electron at the heart of atomic clocks, capable of breaking down one second into 9'192'631'770 oscillations. A time which this time exceeds us, not by its size but by its smallness and by its speed. The speed of machines is not the speed of Nature. Balance is also sought in these time scales and in a synchronization with natural phenomena. The cycle of the tides, the rhythm of the surf that inexorably covers and discovers the foreshore, this in-between world, this blurred transition between sea and land, is at the foundation of the richness of Breton culture. Armor, Arvor, Argoat. From the sea, the coastline, the land. These three terms designate the three worlds that shape each Breton. Breton of the lands, Breton of the seas. Two dimensions of the same culture, which intermingle like the waters in the heart of an estuary. This mixture, this balance, is at the heart of the Gwilen project, enhancing what comes from the sea to build the land. Preserving fragile marine ecosystems while limiting the consumption of land resources. Soothing the complex relationship that our marine infrastructures have with natural environments, to produce this artificial stone, this armor concrete produced as a sedimentary stone by a process inspired by a natural process, that of diagenesis, which transforms particles into rock. A mineral material, made of the clay that has shaped men. Made of these marine minerals that are found at the heart of our cells to which they give all their vitality. The balance always, between the objective and the means, the best way to be inspired by Nature which in performance means optimization: of means, resources, energy. Optimization, the Grail of the engineer who, through his modeling and anticipation, creates systems, micro-worlds inspired by the World. To err between performance and optimization is to think that records allow us to surpass matter. To neglect optimization is to forget that we live in a finite world. Optimizing resources and means, to reach a sufficiency, a necessity. To aim right, to avoid excess. To use what we have to avoid taking what is. To respect time, the geological time which exceeds us and which we violate by an indecent pretension. To respect matter for what it is, and to use it for what it is worth. To work it, and to give it life by necessity. To integrate also the scale of a territory by considering the resources where they are. Designing with what exists, like Levi-Straussian tinkerers, and designing from the world rather than subjecting it to our thoughts and concepts, in a rediscovered balance with our environment.