Melting blue glacier cave

Venture past a certain elevation and it seems that the mighty Alps are a land of everlasting winter, but don't take the chill for granted. We're peering out from the inside of an Alpine glacier cave as a cross-country skier surveys its open mouth—a portal to a frozen fantasy world that's slowly disappearing. Since its position was first recorded more than a century and a half ago, this massive patch of ice—northern Italy's Forni Glacier—has retreated about 2 miles, losing about half its volume. Unfortunately, this isn't a unique predicament among Alpine glaciers: Virtually all are in retreat, and without interventions to slow climate change, as much as two-thirds of the Alps' ice mass is projected to melt by 2100.