Successfully complete the game. You can now fast travel to all the main areas (Slums, Old Town, Antenna). To fast travel between the Slums and Old Town, go to your bedroom in the tower. Use the poster on the wall to instantly travel to the other area. To fast travel to the Antenna area, use the door in the north of the Slums or the sewer entrance in the north of Old Town. You can also return to the sewers if desired through the access points marked on the map at the same locations as found during the story missions.