Here is a few images of Brasilia from the local TV Tower, it shows the "Retornos" very well - these do away with the need for Traffic Lights.

In the bottom picture the road is in three levels. 1st Car Park; 2nd Bus Station; 3rd Main Road through the city. The twin towers at the bottom of the picture is the Federal Parliment and the sky scrapers on either side are all the governmant departments.