I found this fascinating account in the Guardian.
The snow that falls on the Sierra Nevada each year is vital for the economy of Granada, bringing skiers in their thousands and providing a substantial winter income for hotels, restaurants and shops as well as the ski station itself. If not enough snow falls, machines that can manufacture artificial snow are brought in to ensure business as usual.
When it melts, snow feeds the rivers and fills the irrigation channels built by the Moors to water the land. But for centuries, snow from the mountains played another essential role: keeping the city cool in summer. Before the days of refrigeration, teams of men would set out to climb the peaks of the Sierra Nevada to provide the city with ice.
Being mostly illiterate, these men left no account of their expeditions. It was the botanists and later travellers in the 19th century who documented their encounters with the "snowmen". They described how the men would set out in the early hours, accompanied by mules, and climb steadily until late afternoon, singing as they walked; and how in the summer months they would have to ascend the very highest peaks – well over 3,000 metres – to find enough snow.
Then they would set to work with picks and shovels, filling their panniers with up to 150kg of snow. At sunset they would begin the long trek down, covering the panniers with blankets to stop the snow melting. By dawn the men would be back in Granada, where the ice-sellers could begin their distribution.
Their role in keeping the city cool was essential for hundreds of years. The first blow to the “snowmen” came when the local council monopolised and sold off what was once a free activity – the right to extract snow from the Sierra Nevada and sell it. Then in the early 20th century, an ice factory was established in the city. Cheap artificial ice-cubes replaced the snow that the men brought down from the mountains..
The Sierra Nevada is now a national park, and the path taken for centuries by the snowmen is used instead by walkers for recreation – to enable them to enjoy the spectacular scenery.