More on the world's largest offices:

Pentagon

The largest office building in the world. We are know who works at the Pentagon - we just can't talk about it.This massive structure accommodates about 26,000 workers - it has 5 sides, 5 floors above ground, 2 underground levels and 5 ring corridors per floors stretching to about 28.2km of corridor length - a mini-city!

Compare the Pentagon with the massive Merchandise Mart of Chicago

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FCA US LLC Headquarters and Technology Center

.At second, with 490,000 m² of floor area, is the FCA US LLC Headquarters and Technology Center - also the North American HQ and main research and development facility of Chrysler ( FCA stands for Fiat Chrysler Automobiles ). The 15-story building, built at a cost of 1.6 billion, accommodates about 15,000 workers. View this tour of the FCA HQ in the introductory view (source: youtube/mrclassicman)

Compare FCA US LLC HQ (2^nd largest office building) with Place du Portage (3^rd largest building)

Place du Portage

In close third, at 462,636 m², is the Place du Portage building of Canada. The Place du Portage (made up of Place du Portage I, II, III, IV and Place d'Accueil) is a commercial office building can accommodate approximately 10,000 office workers, housing staff from government agencies such as the Canadian Intellectual Property Office and the Competition Bureau in Place du Portage I, Public Services and Procurement Canada in Place du Portage III and Employment and Social Development Canada in Place du Portage IV.

Compare the two largest office buildings of Canada - Place du Portage of Gatineau and Desjardins Complex of Montreal

Place du Portage I et II (source: Wikipedia/Jeangagnon under CC-BY-SA 4.0)

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One World Trade Center.

The One World Trade Center, or 1WTC, is the tallest building in the United States and the seventh-tallest in the world. The 1WTC is the world's tallest all-office building, standing at 541 meters, with 104 floors. Some of its reputed tenants include the State of New York, and Condé Nast Publications.