The only natural border around mainland Britain is the one you get wet trying to cross.
Its only domestic border is a short connection in the west with Okavango.
It remains the only legal border crossing from Norway to Russia till this day.
That fellow had no flexibility at all, yet here he is at the only major border crossing to a town dependent on tourists.
Foreign travel is cherished by East Germans, and the closing of the only border they were able to cross freely had been a serious blow.
Apparently, the only border (somewhat) open from Ethiopia is the one to Djibouti.
Still, even here at the only border crossing from Jordan, there were early signs of war.
Los Indios hosts the only border crossing allowed for use by transmigrantes.
The only foreign border of the governorate was Persia, in the south.
The only safe border from Iraq's point of view is with Jordan.