All humans and animals need water – hence many settlements and civilizations have been built near rivers or water sources e,g the Nile, the Punjab, the Ganges and desert oases. Valleys are also a favoured location because of milder climatic conditions, ease of travel and fertility of soil. The converse is that very few people live in the South Pole because of the harsh weather conditions or on mountain ranges.) Fertile plains which make agriculture possible and so provide the basic need for food are a third category; examples are the Mississsippi delta and the Ganges delta. The need for food can even outweigh other factors: some cities are built near volcanoes because of the rich larva soil despite the dangers of volcanic eruptions.