The largest office building in the world is the Pentagon, located in Arlington, Virginia, United States. Here is a detailed explanation of this iconic structure:

1. Overview of the Pentagon:
- The Pentagon is the headquarters of the United States Department of Defense.
- It is a five-sided building with a total floor area of about 6.5 million square feet.
- The building covers approximately 29 acres of land.
- The Pentagon was completed in 1943 and has since become an enduring symbol of the U.S. military.

2. Architectural Design:
- The Pentagon was designed by architect George Bergstrom and built by contractor John McShain.
- The building features a unique pentagonal shape, hence its name.
- It consists of five concentric rings, labeled A to E, with ten corridors radiating from the central courtyard.
- Each floor has five sections, and the building rises to a height of five stories.
- The exterior is clad in precast concrete panels, giving it a distinctive appearance.

3. Layout and Organization:
- The Pentagon houses various military offices, departments, and agencies.
- It accommodates around 26,000 personnel, including both military and civilian employees.
- Each of the five floors is designated for specific functions, such as administration, intelligence, logistics, and operations.
- The central courtyard, known as the Pentagon Center Court, serves as a hub connecting the various sections.

4. Security Measures:
- Given its critical role in the defense of the United States, the Pentagon is heavily fortified.
- Security measures include restricted access points, security checkpoints, and surveillance systems.
- The building is protected by the Pentagon Force Protection Agency, ensuring the safety of its occupants.

5. Historical Significance:
- The Pentagon has played a vital role in U.S. military operations and decision-making.
- It was a target of the September 11, 2001 terrorist attacks when a hijacked plane crashed into one of its sections.
- Extensive renovations and repairs were carried out following the attack, and the building stands as a symbol of resilience.

In conclusion, the Pentagon is the largest office building in the world, serving as the headquarters of the U.S. Department of Defense. Its unique design, massive size, and historical significance make it an iconic structure.

Pentagon.