"Cities" consists of 16 tiles. These tiles are roads, cities (tiles with roads and houses in the middle) and grass. The tile with only grass is called blank. The tiles are supposed to be arranged in such a way that they fulfil three demands. These demands are: 1. The number of roads leading out of the game plan must be the same as the number of neighbors. The number of neighbors varies depending on the puzzle. 2. All roads must connect to another road or lead out of the game plan. 3. All bricks except the blank must be connected with each other.