This winning entry for the new National Technological Center dedicated to radioactive waste decommissioning was developed following a simple but effective concept: while radioactive substances are brought back to their “hellish” underground belonging, there is an opportunity to restore an “Edenic” condition on the surface. A marvelous garden where a “citadel” – designed like a mountain, featuring an inner “valley” – hosts the Center’s activities. Planting dissolves into the surrounding landscape and the garden/citadel/lake/forest sequence provides all the needed environmental and architectural complexity.