During the game, the city is expanding continuously. Players can erect new buildings. There are three types of buildings: offices (computers), pubs (beer) and houses.

Just as in the case of line expansion and new passengers, the first player to choose this action (so the one on a) must erect as many buildings as the maximum number of buses. The second player to choose this action erects one less building, etcetera. Note that these players will have their turns in reverse order, the player on square a being the last one to erect his/her buildings.

A building may be put on a free building location (white square) on the board. You are free to choose which kinds of buildings you build. At first, only the A-locations may be built. Only when all the A-locations have been filled may the B-locations be used. If they are all full, the C-locations become available. When they too have all been built over, you may start using D-locations. If there are no more free locations, the game ends at the end of the current round.