In one of the many fjords on the South coast of Greenland, there is what Europeans have baptized the "Thumbnail", a one-mile-high granite wall, undeniably the tallest cliff on the planet. Cecilia and Roberta, two of the best mountain climbers in the world today, prepare to ascend. They approach the wall by kayak, rowing for several days through icebergs, passing whales and seals: an incredible scene of the serenity of nature.