The architectural project as it was set out in the competition rules had to meet criteria of interdisciplinarity, freedom of movement & flow and an open approach to exhibition areas. The competition was won by two young architects: the italian Renzo Piano and the british designer Richard Rogers, who proposed an architecture freed from constraints and in the vein of the 60s' spirit. The supporting structure and movement & flow systems such as the escalators were relegated to the outside of the building, thereby freeing interior space for museum and activity areas. Secured to the external west façade of the building and constituting "dressing " for the structure, the technical ducting featured four colors: blue for air, green for fluids, yellow for electrical sheaths and red for movement & flow. The transparent nature of the west main façade makes for an outside-looking-in approach which enables people to see, from the piazza, what is going on inside the Center. The piazza is a vast esplanade which the architects conceived as a continuity zone linking city and center.