Ram, there is no such thing like "the best" lens.
It depends much on what's you expectation about it and what kind of a landscape shots you'll be trying to shoot.
You can get some nice results both with wide angle lenses and telephoto ones, but for the beggining I would recommend something wider.
First of all - please tell me what kind of a camera are you using (is it Nikon D200?) and what is your budget ?