The Mont Blanc glacier is one of Europe’s best known landmarks. But now it is under threat.
Work has begun to drain a huge lake that has formed under the ice which it is feared could endanger both the glacier itself and residents living further down the mountain.
It is something the town of Saint Gervais has already experienced.
Mayor Jean-Marc Peilleix explained: “The danger is that if the ice breaks the water will cascade down to St Gervais from a height of 3,200 metres to the lowest point of 580 metres and we would have a repetition of the 1892 scenario.”
Almost 200 people were killed then.
Scientists estimate the amount of water trapped under the glacier to be the equivalent of 26 Olympic-sized swimming pools.
They have been seeking to reassure locals they have the situation under control and they seem to have had some success.
“We’re not really worried,” one man told reporters. “We are watching events but I would say we have faith in that the work is under way.”
However there are risks and others have left their homes while the work is carried out.
The final section of the Mont Blanc tramway has also been closed.