The world of Cittàgazze was one of many parallel universes. Cittàgazze and Sant'Elia were two of the towns in this world. It was known as the crossroads between worlds because all windows between worlds led to this world, which is because this world is where the subtle knife was created. However, Lord Asriel's disturbance to the magnetic poles allowed other worlds to open into other worlds without going through this world.
The world appeared to be quite modern; electric lights and fridges were used. Spectres were common in this world for several generations, however their number was greatly multiplied after Lord Asriel created a huge window through his world into that of Cittàgazze.