Nanjing is an old city.It has many interests.Some of them have existed for hundreds years.One of them is Ming City Wall.It was built in Ming Dynasty.In order to defend the invaders,the emperor of Ming Dynasty built the wall. Nanjing is an old city.It has many interests.Some of them have existed for hundreds years.One of them is Ming City Wall.It was built in Ming Dynasty.In order to defend the invaders,the emperor of Ming Dynasty built the wall.