The criteria for the choice of settlements as urban centre in different parts of the world are varied. These are population threshold, legal/administrative and the functions performed by settlements. These criteria have their challenges in the development of settlements themselves and in the surrounding ones in various regions. The book explores these criteria, adopts a rational and comprehensive one based on functions performed by settlements and develops a model for ranking and developing them. The book is recommended to policy makers and development planners especially in the developing regions of the world. In addition to the above, it provides researchers a basis for comparison between how urban centres in developing regions and the developed world are designated.