Standing at the rail of the Glacier Queen, we were riveted to the face of the 300-foot-high wall of ice towering before us. Though it was a quarter-mile away, we could hear every crack and crumble as the active tidewater glacier heaved and sloughed ice into the frigid waters of Prince William Sound.

The final leg of my race across the great desert of Antarctica ended Friday, and with it, the conclusion of an amazing adventure that has spanned many years.

A friend once said to me "Len, you'll never be a runner." When I cross the finish line in Antarctica next month, I can officially say I've proven him wrong!

I suffer from an addiction to travel and adventure. So this post is in essence adventure geekery, an attempt to define the undefinable -- the best adventures on Earth.