The present logic of built environment dispersion appears incompatible with the concept of sustainable development. The peripheral expansion of cities is indeed leading to irrational use of ground, growing environmental impact and important infrastructure costs. Looked at from this point of view, the Ecoparc project consists in promoting the sustainable regeneration of an urban wasteland of almost 4 ha, located next to Neuchâtel railway station and notably including the Federal Office of Statistics (FOS) buildings. The design process is based on constant optimization between environmental, socio-cultural and economic criteria, notably by coherent integration of contemporary architectural expression, reduced energy consumption (mobility, infrastructures, buildings) and functional synergies.