Our project in Maine-Montparnasse seeks to transform this Parisian neighborhood into a green pilot site. The ambitious, sustainability-focused initiative expands the planted environment into a biodiverse ecosystem, while implementing a low-carbon approach: 2,000 new trees stretch across 10,000 square meters of green space, in a bioclimatic design centered on energy exchange, circular economy practices, and maximum preservation and reuse of existing infrastructure. The road network is reimagined to prioritize pedestrians, active mobility, and public transportation, with new, uninterrupted rows of trees and lush greenery lining the redesigned streets. The zone around the Montparnasse train station provides the perfect canvas for an urban forest, even with its vast network of underground infrastructure. This infrastructure was thoroughly analyzed in order to design this new public space, shaping a composition that deftly balances dense vegetation with high levels of user traffic. Careful grading at surface level ensures that subsurface structures are flush with the ground and existing thresholds remain level, while increasing accessibility for users of all mobility needs. This grading also directs stormwater toward planted softscape, implementing resilient water management throughout the site. The result is a continuous surface free of obstacles and disruptions, laying the groundwork for this new, legible, and simplified public space – one designed to both streamline heavy user traffic and provide comfortable and shaded spaces for rest.