In previous eras, most of the world's major cities had a trait that few retain today: a fortified wall. Once necessary for protection, these barriers kept citizens safe from outside forces. As weapon technology advanced, walls become less and less important. They often turned into a hindrance for people living inside the city, and most of them were torn down. A few remain, having been absorbed into the modern landscape, like the imposing walls of Xian, pictured.
Here are 10 examples of historic city walls that are still standing today.