Roji is a tiny alleyway between houses. You may see this kind of alleyway in many towns that are crowded with houses throughout Japan as well as in other parts of the world, but, to me, roji are always a reminder of Kyoto. In midtown Kyoto, the streets are set out neatly in grid. The shorter side of the grid square is about 50 meters long and the longer side about 100 meters or longer, and typically there are 40 to 50 houses within one grid box. That's why you need many narrow alleyways to reach houses inside the box.