Ageing populations are a major feature of social and economic life globally, with the world's population aged 60 years and over expected to reach 21% and around 2.1 billion people by 2050. In 2018, 18% of the UK population were aged 65 and over. This is expected to reach 23% (approximately 16 million) by 2035. South Korea has one of the most aged populations in Asia with the number of people aged 65 or older expected to reach 15 million, accounting for 30% of the population in 2035. The combination of an ageing population with reduced levels of fertility presents challenges to individuals, families, and society as a whole: as the nuclear family is shrinking dramatically, the role of the family is also changing. The traditional family structure, where the care of older people relies heavily on younger family members, comes under pressure. It highlights concerns that the ageing demographic transition could pose a drag on the country's economy and negatively impact public finances and standards of living. These fundamental changes in the age and family structures have important implications for the whole of society: the way older people live; the house and community they live in; care for older people; and the way older and younger generations integrate. Urbanisation is another phenomenon that most countries have experienced over the past half-century. In 1950 just 30% of the world's population lived in cities and towns but the proportion increased to 56% by 2020; and it is expected to continue to grow to 66% of the world's population, almost 10 billion inhabitants, being urban dwellers by 2050. Urbanisation has been taking place rapidly particularly in the UK and South Korea, with 84% and 81% of the respective populations living. The growth of older people living in urban settings, in particular the large urban areas, is growing faster than the total population. While urban areas offer better facilities and closer proximity to public services and can potentially provide a better quality of life to the older population, the challenges that they face are even greater than before: the higher proportion of older people has put great strain on public spending, with growing pressure on health services and social welfare. In this context, cities have become both parts of the problem and part of the solution to the healthy ageing challenges of the 21st century to provide better services and create supportive environments for older people to thrive. To tackle the urban ageing agenda, nearly two decades ago the World Health Organization (WHO) published the Global Age-Friendly Cities Guide and a companion 'Checklist of Essential Features of Age-Friendly Cities'. The features of age-friendly cities are determined in eight domains of urban life: outdoor spaces and buildings; housing; transportation; civic participation and employment; communication and information; community support and health services; social participation; and respect and social inclusion. Although the age-friendly city perspective has been influential in raising awareness about the impact of ageing, many urban areas are not always the most old-age friendly. Since then, the value of the approach has been assessed in the context of contemporary cities affected by pressures associated with global social, economic and health care changes. South Korea and the UK have already been active in moving toward this direction with 32 cities in South Korea and 32 areas in the UK having already been involved as members of 'WHO Global Network for Age-friendly Cities and Communities' established in 2010. However, much remains to be done and the proposed network will contribute towards achieving the WHO vision and objectives.