It shall be unlawful for any person to construct or maintain any stairway, open cellarway, open basement way or open entrance thereto in or adjacent to any sidewalk, pavement or street, and any such entrance is hereby declared to be a public nuisance; provided, all existing stairways, open cellarways, open basement ways or open entrances thereto in said sidewalks, pavements or streets may be permitted to remain from and after the passage, approval and publication of this code if said person owning or using said opening in the sidewalk or street shall satisfy the Building Official that the same is properly protected by a balustrade or coping of durable material, and shall furnish the city with a bond in such amount as the City Council may set, for the benefit of any person who might suffer an injury or damage by reason of the use of said stairway, cellarway or open basement way.