The pentagon...The name alone conjures up an imposing image of American power and prestige. As the largest office building in the world, it serves as the headquarters of the nation's armed forces. Every day, more than 24,000 men and women come here to work on the vital and sometimes top secret business of national defense. Beyond the pentagon's massive size and awesome purpose looms its impenetrable mystique. We'll take you inside this military institution, national symbol, and modern marvel.