This paper proposes a new definition of sub-centers. Density of workers is complemented with the observation of four approaches for the analysis of the Barcelona Metropolitan Area. These four approaches are the urban lands paterns (based on CORINE land cover information), the mobility of workers (from data of the Spanish Census), electric consumption (from information of the electric companies) and the estimated CO2 production. Consequently, the urban structure will be defined based on these four approaches, which also will validate the reviously defined 15 subcenters of the Barcelona Metropolitan Area.