Reply #1: could this be a reason? [View All]

[Fleshdancer]

I don't know if this is the exact reason, but it's a good guess:

Stripped of its occupants, furniture and various decorations, the building alone is an extraordinary structure. Built during the early years of World War II, it is still thought of as one of the most efficient office buildings in the world. Despite 17.5 miles of corridors it takes only seven minutes to walk between any two points in the building.

http://www.defenselink.mil/pubs/pentagon/about.html