Parapet walls and false mansards shall not extend more than six feet above the height in limit. Flagpoles, chimneys, cooling towers, electric display signs, elevator bulkheads, penthouses, finials, gas tanks, grain elevators, stacks, storage towers, radio, television, or microwave towers, ornamental towers, monuments, cupolas, domes, spires, standpipes, and necessary mechanical appurtenances may be erected as to height in accordance with the existing or hereafter adopted ordinances of the City of Garden City, Missouri.