History (and sometimes, unfortunately, current events) shows us just how easily national borders can change, but we still like to think that they are permanent fixtures. These photos of different national borders around the world show you how both friendly and hostile nations like to fence off their turf.
Borders can make for some striking manifestations of power on the landscape. On the other hand as seen in this picture of Slovakia, Austria and Hungary, friendship and cooperation can also be inscribed into the landscape. There are some great teaching images in this gallery.