For thousands of years, humans have built walls and assaulted them, admired walls and reviled them. Great Walls have appeared on nearly every continent, accompanying the rise of cities, nations, and empires. In Walls, David Frye uncovers a story that is more than just bricks and stone: he 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 civilization...