A rainbow over the horizon transfixes an Alaskan fisherman hunting in Norton Sound, Alaska, part of the mouth of the Yukon River. The 2,000-mile-long (3,200-kilometer-long) river empties into a delta bigger than Texas that teems with wildlife including crab, seal, and salmon.

(Photo shot on assignment for, but not published in, "The Untamed Yukon River," July 1998, National Geographic magazine)