When walking in the fortress at Montjuic in Barcelona I found at the wall of the tower a small plaque and a sundial. Reference was made to Pierre Mechain who set out to measure the meridian arc distance between Dunkirk to Barcelona. The fortress was chosen a the reference point. Using this measurement and the latitudes of the two cities he could calculate the distance between the North Pole and the Equator and produce the first prototype "Metre" which was defined as 1/10.000.000 of that distance.
Sundial reference the coordinates.
Fortress on Monjuic in Barcelona
