Europe's highest summit has two maps: Rome draws the border across the top of Mont Blanc, Paris puts the whole peak in France
Above Courmayeur, in Italy's Aosta Valley, the summit of Mont Blanc, 4,807.3 metres at the latest survey in 2025, sits on a line that two countries draw differently. A bilateral agreement of 1861, still legally valid, makes the summit itself the frontier, shared half and half; but in 1865 a French map by Captain Mieulet moved the line and enclosed the top in France. Since then Italy's Istituto Geografico Militare has kept the border along the crest, the French IGN puts the whole peak on its side, and Swiss maps simply mark the area as disputed. On the ground, from the Torino hut up to the summit, Italian authorities are in charge. Nobody has ever settled it.
