Mendenhall Glacier, a 12-mile-long mass of ice in Juneau, Alaska, is a popular tourist attraction. Few visitors, however, see the the glacier from its most spectacular vantage point: inside it. A trip to the Mendenhall ice caves requires an arduous journey - it involves a kayak ride or long hike, an ice climb, and faith that the melting caverns won't collapse in on you - but the incredible landscapes are a once-in-a-lifetime sight.