For starters, a moderate wide angle would be a wise choice. Specifically which focal length is determined by the format of the camera - 35mm, medium, or large format cameras.
If it's 35 mm, then a fixed focal length anywhere around 24 would be fine. Wide angle to short tele-zooms are convenient so an 18-70 or -28-70 mm might be advisable. However, if you want to capture mountainous landscapes or add wildlife too, then use of a telephoto or a tele-zoom... then you might want a 28-200 mm if a tele-zoom.
Also, it's a must to use a tripod if you want sharp images.