The supportive role of urban spaces in active aging is explored on a world scale in this unique resource, using the WHO's Age-Friendly Cities and Community model. Case studies from the U.S., Canada, Australia, Hong Kong, and elsewhere demonstrate how the model translates to fit diverse social, political, and economic realities across cultures and continents, ways age-friendly programs promote senior empowerment, and how their value can be effectively assessed. Age-friendly criteria for communities are defined and critiqued while extensive empirical data describe challenges as they affect...