The impact of certain physical features, such as land forms, climates, and natural vegetation. If you live in the mountains, you're likely to develop a particular culture that adapts to life at a high altitude.
Depending on where you live, you can practice different customs. For example, people who still continue to live in tribes and do not have access to technological advances as the more developed worlds will still hunt and gather and live according to what they have available. Another way it impacts culture is that when you live in one area with better natural resources or natural barriers against foreign attacks you are safer and are more able to protect your country.
