Yellowstone's crowds disappear in the winter, and the park takes on a whole new vibe when it's covered in snow. SeeYellowstone (seeyellowstone.com) offers all-day snowmobile and snowcat tours. My friends and I signed up for one and spotted these bison stopping for a drink in the chilly river. We also came across moose, bald eagles, a coyote, elk, and some grizzly tracks.