For thousands of years, humans have been defending their cities by building huge walls around them. Over time, the cities often spill over the walls - but sometimes they remain hemmed in. Here are some incredible images that show what happens to walled cities over time.
For thousands of years, humans have been defending their cities by building huge walls around them. Over time, the cities often spill over the walls - but sometimes they remain hemmed in. Here are some incredible images that show what happens to walled cities over time.