The purpose of Marietta's historic preservation ordinance is to protect and enhance the historical and aesthetic attraction to tourists and visitors and thereby promote and stimulate business, and to provide for the protection, enhancement, perpetuation, and use of places, districts, sites, buildings, structures, and works of art having a special historic, architectural, cultural, or aesthetic interest or value, and to provide reasonable flexibility for property owners to improve and maintain their properties below certain thresholds and for special circumstances.