10 most visited spots in the National Park System

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People walk in front of the Lincoln Memorial as a heavy snow storm hits Washington D.C. on February 13, 2014.

John D. Simmons / McClatchy-Tribune

A train of six veteran llamas goes under Grotto Falls on the Trillium Gap Trail heading up to LeConte Lodge in the Great Smoky Mountains National Park, April 21, 2009.

Chicago Tribune

The Delware River gap in Pennsylvania along the Appalachian Trail.