The stark regions of the Arctic and Antarctica are a testament to the limits of life itself. At the most remote ends of the Earth, visitors are astounded by the alternating absence of daylight and darkness, vast expanses of ice and frozen tundra, and rare glimpses of polar bears, seals, and migratory whales. Travelers come to experience the extremes of these landscapes, and to bear witness to the fragility of existence here in the face of climate change.