Which is the biggest building in the world?

The tallest man-made structure is Burj Khalifa, a skyscraper in Dubai that reached 828 m (2,717 ft) in height on 17 January 2009
The biggest building in the world is the worlds Dubai
Aircraft assembly plants are the largest buildings in the world based on sheer volume; the Boeing plant is the largest of these building types.

In terms of floor space, the Dubai International Airport's terminal 3 is the largest in the world.

In terms of height, the Burj Khalifa is the tallest building.