The great hollows of the Gavarnie, Gèdre and Pragnères basins were gouged out by glaciers. The waters sliced through the rock between the basins to create "narrows", the most typical of which is St-Sauveur Gorge. Temporary dwellings perch on the resulting ledges; torrents rush down in cascades from tributary valleys. The austerity of the landscape inspired George Sand to write: "From Luz to Gavarnie is primeval chaos; it is hell itself"!