This book discusses existing and future global problems of physical, chemical, biological and societal origins faced by increasingly populated cities and mega-cities, and options to mitigate or eliminate them. In nine chapters, the book focuses on rehabilitation and redevelopment projects aimed at converting shantytowns/slums into well serviced neighborhoods via secure housing, clean piped water, adequate access to sanitation, and other amenities for good living conditions. Examples of rehabilitation (restore capacity, structures, efficiency) and redevelopment (redesign, rebuild, attract investment) are addressed in detail, as are the sources of major financing to support such projects and proposals. The final chapters also discuss problems faced by countries with contracting populations, and their viable solutions. The book will be of interest to academics, city planners, land-use planners, NGOs, and designers /architects specializing in urban development and redevelopment.