The breathtaking Blue Line of France's Vosges mountains
We head to eastern France to discover the "blue line" of the Vosges mountains, running along the pre-1918 Franco-German border. It was named by the 19th century statesman Jules Ferry, and separated the Vosges from the annexed Alsace-Lorraine region. The ridge can be seen much more clearly from the air - we meet some lucky tourists taking a balloon ride over the peaks. The area was also the scene of heavy fighting during World War I: we meet locals keeping the memory of the fallen soldiers alive.