In northern Spain's Cantabrian Mountains, winter regularly buries the landscape in snow, yet step inside one of the region's limestone caves and the atmosphere feels almost calm, mild and strangely untouched by the storm raging just metres above. This is not a quirk unique to Spain; caves around the world are famous for staying remarkably stable no matter what the surface weather is doing, but the Cantabrian caves offer a particularly striking example simply because the contrast with the snow-covered slopes outside is so dramatic.