As the opening date of the Brussels World's Fair nears, the elaborate pavilions of the 48 nations taking part are rushed to completion. America's building, the world's largest freestanding circular structure, will be an architectural landmark. Scores of international and commercial groups are also taking part in the rivalry for the attention of the 40 million visitors expected. One of the commercial exhibits is a vast diorama of the Belgian countryside, which will model a prophecy of progress in transportation. Under a complex electronic control system, a diorama will show the transformation from today into the world of the future. The Atomium, fitting symbol for the first World Fair of the Atomic Age.