In December 2000, the Old City of Baku, including the Palace of the Shirvanshahs and Maiden Tower, became the first location in Azerbaijan to be classified as a world heritage site by UNESCO. It is widely accepted that the Old City, including its Maiden Tower, dates back to the 12th century, with some researchers contending that construction dates as far back as the seventh century. The question has not been completely settled. It was during this period that Baku started to extend beyond the city walls, and new neighborhoods emerged. Thus the terms Inner City and Outer City came into use.