The Pentagon

The Pentagon:
Construction began: September 11, 1941
Construction completed: January 15, 1943
Complex: 34 acres: building covers 29 acres; inner courtyard covers 5 acres;
Dimensions: 77 feet high; each wall is 921 feet long;
Walls: 24 inches thick - 6 inches of Indiana limestone; 8 inches of brick; 10 inches of concrete
Space: 3,705,793 square feet of office space on five floors; 17.5 miles of corridors;
Elevators: 13
Escalators: 19
Stairways: 131
Workers: 23,000

The Pentagon is constructed in five concentric rings connected by ten spoke-like corridors. It is in the midst of its first renovation since its construction in 1941. The extensive renovation began in 1998.

The renovated sections included new designs to minimize the damage from an explosion:
1. Steel Beams were installed on each side of every exterior window
2. A strong mesh material, similar to Kevlar, was stretched between the beams to catch flying debris.
3. New blast-resistant windows were installed. The panes were an inch and a half thick and each window weighs 1,600 pounds.
List of September 11th Victims