<p><em>This story is part of <a href="http://news.nationalgeographic.com/news/clean_water_crisis.html">a special National Geographic News series</a> on global water issues.</em></p><p>A Hindu pilgrim worships in front of an ice stalagmite, or lingam, in a cave in Kashmir during the annual Amarnath Yatra. Between May and August each year, hundreds of thousands of Hindus make the <em>yatra</em>, or pilgrimage, to a remote cave in the Himalaya, to see the phallic ice structure that they believe is the mark of the god Shiva. (See "<a href="http://news.nationalgeographic.com/2012/03/120312-hindu-pilgrimage-stresses-fragile-himalaya-environment/">Massive Hindu Pilgrimage Melting Sacred Glacier</a>")</p><p>The cave is one of the most revered of Hindu shrines, yet the ice stalagmite is melting, in part because of climate change, but also because of the body heat of so many visitors, scientists say. Traditionally, pilgrims arrived on foot or on horseback, picking their way along 30 miles of trail over glaciers and through mountain passes. But increasingly, wealthy visitors have been taking helicopter rides to the site, with a frequency of 300 flights a day.</p><p>Ecologists have warned that trash and waste from so many visitors is damaging the fragile alpine environment, which also serves as the headwaters of the vital Indus River.</p><p><em>—Brian Clark Howard</em></p>