At 3,664,883 cubic meters (129,428,000 cubic feet) it is one of the largest buildings in the world by volume. The building is at Launch Complex 39 at KSC, halfway between Jacksonville and Miami, and due east of Orlando on Merritt Island on the Atlantic coast of Florida.
The VAB is the largest single-story building in the world, was the tallest building (160.3 meters, 526 ft) in Florida until 1974, and is still the tallest building in the United States outside an urban area.
The VAB, which was completed in 1966, was originally built to allow for the vertical assembly of the Saturn V rocket for the Apollo program and referred to as the Vertical Assembly Building. In anticipation of post-Saturn projects such as the Space Shuttle program, it was renamed the Vehicle Assembly Building in 1965, and was used for the shuttle's external fuel tanks and flight hardware, and to mate the Space Shuttle orbiters to their solid rocket boosters and external fuel tanks. Once assembled, the complete Space Shuttle was moved on the Mobile Launcher Platform and Crawler-Transporter to LC-39 Pad A or B.
There are four entries to the bays located inside the building, which are the four largest doors in the world. Each door is 456 feet (139.0 m) high, has 7 vertical panels and 4 horizontal panels, and takes 45 minutes to completely open or close. The north entry that leads to the transfer aisle was widened by 40 feet (12.2 m) to allow entry of the shuttle orbiter. A central slot at the north entry allowed for passage of the orbiter's vertical stabilizer.
According to wikipedia