At one time the biggest building in the world, and still in the top 5 I believe, this is a very impressive place. The airfield was originally designed for a small airport, but Hitler decided to create a huge, imposing building which could transport millions of people per year and could be the site of massive airshows that the whole city could come watch. In the Cold War, the Russians blocked all road transit and this airport was the exclusive location for the US and others to land with supplies in Berlin. At its peak there was a plane flying in or out every 3 minutes to ensure that the population have whatever they needed.
