You’ve undoubtedly heard talk of building a wall along the southern border of the U.S. While the effectiveness of a wall is debatable in the context of the 21st century, the topic calls to mind some famous walls built throughout human history. One of the best things about travel is it gives us the chance to reflect on where we are, where we’ve come from and where we’re going. Though the walls listed below are no longer used for their original purposes, they still hold great significance as symbols of heritage and a past that should not be forgotten. They remind us that boundaries divide, while travel unites.