When considering zoom lenses for landscape photography, many photographers only choose wide angle lenses and automatically eliminate long focal length lenses. While certainly not the only choice or even the first choice for landscape, the 70-200mm range lenses are a great adjunct to a landscape kit. I personally like the f/4 versions because they are smaller, lighter and considerably less expensive and I do not necessarily need an f/2.8 aperture for landscape work. I generally shoot around f/8 or f/11 for landscapes.
BTW: this focal range can be pretty effective for cityscapes also.