In 1956, Costa won the competition of the urban plan project for the city of Brasilia. His close friend Oscar Niemeyer was the chief architect of public buildings, and Roberto Burle Marx was the landscape designer. It started with a sketch sign of the cross that curved from the edges to adapt the topography and the natural drainage in the city, creating a triangle form that meets the limits of the urbanized area. These strong axis lines established the natural access entries to the city, and the curved line shaped the residential spaces. Within the intersection of the vertical and curved axis, the concept started to develop.
Costa did not even choose to run for an office at that time; he simply presented the project as a possible solution to the problem of planning the city. What can be found in his design principle is functionalism, with the administrative facilities and residential areas located on the dragonfly or airplane-shaped design form.