There is hardly any part of the globe in which people have not settled. In some cases the settlement may be no bigger than one or two families and their livestock, in others the settlement may be a city as large as New York. There is always a good reason for a settlement being where it is. If you look in the atlas you will see that most of the world's major cities are located on an important river or on a coastline. This is because they grew up as trading centres, importing and exporting goods to serve their surrounding areas. Inland towns and cities are often at the meeting point of two or more land or river

trading routes. With trade comes prosperity, so towns and cities can support increasing populations. Agricultural settlements - farms and villages - need fertile soil and a supply of water for both crops and drinking. River valleys have both, and so are often densely settled - a large proportion of India's population, for example, lives in the plain of the Ganges river. Another factor determining the sitting of a settlement is that it can be easily defended against enemy attack in time of war. Many towns and villages were originally founded on hill sites for this reason. 

(from Dougal Dixon : Geography, Franklin Watts)

Question:  If you were taking notes, what heading would you give this passage?