For thousands of years, humans have built walls and assaulted them, admired walls and reviled them. Great walls have appeared on nearly every continent, the handiwork of people from Persia, Rome, China, Central America, and beyond. They have accompanied the rise of cities, nations, and empires. And yet they rarely appear in our history books. Spanning centuries and millennia, drawing on archaeological digs to evidence from Berlin and Hollywood, David Frye uncovers the story of walls and asks questions that are both intriguing and profound. Did walls make civilisation possible? Can we live without them? This is more than a tale of bricks and stone: Frye reveals the startling link between what we build and how we live, who we are and how we came to be. It is nothing less than the story of civilisation.