The owners or occupants of all buildings and real estate within the City shall remove all snow and ice from the public sidewalks adjacent thereto as follows. Each owner or occupant of real estate within the Central Business District shall clear or cause to be cleared all snow or ice from such sidewalks within 12 hours after the snow or ice has ceased to fall thereon. "Central Business District" as used herein includes that part of the City bounded by Highway 61 on the west, Dodge Street on the east, and on the north and south side of Belvidere Avenue County Road 18.