People have been drawing lines on maps for as long as there have been maps to draw on. Sometimes rooted in physical geography, sometimes entirely arbitrary, these lines might often have looked very different if a war or treaty or the decisions of a handful of tired Europeans had gone a different way. By telling the stories of these borders, we can learn a lot about how political identities are shaped, why the world looks the way it does--and about human folly. From the Roman attempts to define the boundaries of civilization, to the secret British-French agreement to carve up the Ottoman Empire during the First World War, to the reason why landlocked Bolivia still maintains a navy, this is a fascinating, witty, and surprising look at the history of the world told through its borders.