General Motors is closing its Willow Run manufacturing plant on December 23, 2010. At 5 million square feet, it's one of the largest buildings in the world. A total of 42,000 people made B-24 bombers at the Ypsilanti Township, Mich., facility during World War II. Here's what it looks like today. This video was produced by AnnArbor.com's Nathan Bomey.