In Badalona, small city in the periphery of Barcelona, it was necessary to create a new centrality and at the same time to solve severe mobility problems. The proposal consisted of a maximum concentration of ecological dwelling, offices and commerce over a metro station. On one hand, we increased the economical activity in that small central area. On the other hand, we improved the car mobility by the construction of a tunnel increasing ecological sustainability. The city is by definition the concentration of the diversity.