Walking through Berlin today, it can be difficult to imagine a time when crossing from one neighborhood to another was forbidden. Streets, railway lines and public spaces now connect places that were once separated by a heavily guarded border. Yet the traces remain. A section of concrete, a memorial beside a bridge or a line of cobblestones in the pavement can reveal where the Berlin Wall once stood. On 9 November 1989, the opening of the border transformed the city. Places a