The landscape of a world is important because it helps you set the scene. A mountainous world will be described slightly different than a flat, prairie-like world. Also people may have different ways to deal with different types of landscapes. People in a prairie are more likely to use a horsedrawn carriage than people who live in the mountains. People in the mountains are more likely to ride on the back of horses or just walk on their two feet and use pack animals to carry their belongings because that makes travelling on mountainous roads that much safer.
Travel times are also important as well as how safe routes are at any time of the year. It will take longer to travel through a mountainous area than a prairie, and the roads stop being safe as soon as it snows or rains unlike in a prairie. Of course prairie’s have their own problems with flooding as soon as it rains a good amount in one day.