http://en.wikipedia.org/wiki/Frankfurt_auto_show
This is the world's largest auto show and is held once every two years in Frankfurt, Germany. An estimated 850,000 people came to the vast Frankfurt Messe (nearly a mile from one end to the other) and saw close to 100 different vehicles make their very first first public appearance.
More cool info:
http://www.e90post.com/forums/showthread.php?t=301334 - design and construction of BMW's massive exhibit