16 June 2013 Last updated at 19:50 ET
How Napoleon's semaphore telegraph changed the world
By Hugh Schofield BBC News, Modane, France
"Enthusiasts worked out the probable location by consulting maps in the archives in Paris. In 2002 they found the remains of the post in woods above the village of Sardieres. Now they have just rebuilt an exact replica, using original designs drawn up by an inspector on the line.
Visitors who make it up the brisk climb find a two-room cabin of wood and stone. The second room contains a system of wheels and pulleys, controlling the signal system which is set on a mast above the roof. A panaromic view looks south-east across the valley to more snow-capped mountains. Beyond is Italy."