In September 2003, the Botswana government began to build a 300-mile fence along its border with Zimbabwe, officially as a foot-and-mouth disease control measure. Critics claim the fence in fact serves to discourage the influx of tens of thousands of illegal immigrants from neighboring Zimbabwe. History provides us with many examples around the world — from the Great Wall of China to the Berlin Wall — of structures erected by one group of people with the intention of keeping another group out. View the following pages to explore our map to learn more about some of todays most fascinating border fences.