• Economic powerhouses: Cities fuel a nation's economy.
• Innovation hubs: Cities are often the birthplace of new ideas and technologies.
• Trading epicenters: They serve as crucial trading centers.
• Population growth: Cities are typically areas of high population density.
• Socioeconomic disparities: They can harbor major inequalities.
• Economies of scale: Large populations can create efficiencies in production and services.
• Environmental challenges: Cities have to tackle issues like pollution, congestion, and inflated land prices.

Example: New York City is one of the world's leading economic hubs, but it also struggles with issues like air pollution and socioeconomic disparities.

• Economic productivity: They are economically viable, with robust transport, energy, water, and waste infrastructures.
• Social inclusivity: They promote social mobility, helping to prevent unrest and conflict.
• Environmental friendliness: They seek to reduce their ecological footprint by using less fossil fuel and increasing recycling and reusing efforts.

Example: Amsterdam is known for its cycling culture, efficient public transportation system, and a wide range of initiatives aimed at reducing its environmental footprint.

• Infrastructure Investments: Cities can build infrastructure like tidal barriers and sea walls.
• CO2 Emissions: Densely populated cities tend to produce less CO2 per capita due to potential for better public transport and savings in building heating and cooling.
• Transport Innovation: As cities expand, they can develop new transport systems like metro systems and rapid-transit bus systems.
• Reducing Fossil Fuel Use: Expansion of bus lanes, cycle lanes, footpaths, and bike-sharing schemes can reduce fossil fuel consumption.

Examples: Beijing and Shanghai have developed advanced metro systems. Bike-sharing schemes have been established in Paris (the Velib scheme), Barcelona, and London.

Cities need to provide clean, affordable, and reliable water supplies. For instance, New York sources its water from the Catskill and Croton drainage basins and has financial incentives to prevent pollution.