The world's walls are supposed to be coming down. We speak of globalization, international markets and global villages; barriers to trade keep falling, and it is now possible to communicate instantly from nearly anywhere in the world. But just as these virtual walls come down, real walls rise. In this evocative blend of travel writing, history and politics, Marcello Di Cintio visits the world's most disputed edges to meet those who live alongside the razor wire, concrete and steel.