Los Glaciares

Declared in 1937, it protects the second largest continental ice field outside the polar regions, from which 47 major glaciers descend. The most celebrated, the Perito Moreno — named after the same Francisco Moreno who donated the land for Nahuel Huapi — is one of the few glaciers on the planet holding a remarkable mass balance, advancing and calving spectacularly rather than retreating as the great majority of the world's glaciers are under global warming, which has made it famous with scientists and tourists alike. It has been a UNESCO World Heritage Site since 1981, and every few years it stages a natural rupture, when its advance dams the Brazo Rico arm of Lake Argentino completely and the ice wall breaks apart in front of thousands of onlookers.