Back to the beautiful Halle Pajol and its photovoltaic power plant for the conference organized by Arene Île-de-France on ecological urban planning. An opportunity to go beyond borders with a reasonable carbon footprint to discover German and Swiss experiences showing different approaches to the French model in terms of project governance and land management. In Switzerland, for example, the use of long-term occupancy leases enables a territorial dynamic that is somewhat detached from land speculation, making way for housing cooperatives, for example, which generate social added value. This approach was already discussed during our visit to the Solar Decathlon in Versailles.