Actually, what keeps verticals vertical in large format, is the possibility to keep the film plane parallel to your subject. If you take an image of an house, you want to keep your film plane parallel to the front side of the house.
Using a SLR camera this means to use half of your image to capture the floor. With a large format camera, you can shift up the lens to capture the building and not the floor. This only is possible, because of the large image circle large format lenses create on the film plane. Depending on the lens it's a bit larger than the film, sometimes it's much larger. The larger the image circle, the more freedom for movements.
Hence the Schneider Kreuznach Super Angulon72 is a very hard to get and expensive lens. The dream of every architectural large format photographer.
To get a deeper understanding of large format photography and it's equipment, large format photography info is a great resource. It has a lot of basic information and a forum.