Smithsonian magazine has just announced the winning entries in their 13th annual photo contest, selected from more than 46,000 entries sent in from 168 countries. They've shared the Grand Prize winner here, as well as the winning shots from the competition's six categories: The Natural World, Travel, People, The American Experience, Altered Images, and Mobile. Captions were written by the photographers. Be sure to visit the contest page at Smithsonian.com to see all the photographs from this year.