Overall, the Nordic countries once again dominated the top slots, with Finland coming in as the world's happiest country for the fifth year in a row.
A study shows that most of the happiest cities in the world have high metrics of sustainability.
Various factors were taken into account in determining the subjective measure of well-being, including GDP per capita, life expectancy, social support, freedom to make life choices and generosity.
Top countries, the report states, are found to "support well-being, including income, healthy life expectancy, social support, freedom, trust and generosity."
The happiest country on the list is Finland, with Norway and Sweden also making the top 10.