"Today, just over half of the world's population lives in cities. By the year 2050, this number is expected to grow even more. What's a city, exactly? That depends on who you ask. There's s no internationally accepted definition of a city, but there is no denying that the hustle and bustle of the world's most populated areas are impressive. Some of the world's most famous cities are capital cities, serving as an economic and cultural hubs and as their country's center of government. Some cities are known for their beautiful skylines, while some are known for their sheer number of skyscrapers, known for their cosmopolitan vibes and joie de vivre." Have a nice day!

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The cities of the world are very modern and very exciting. Usually, expenses are more expensive than usual. Some cities of the world are under environmental pollution because vehicles emit harmful gases such as CO, CO2, NO2,...causing the greenhouse effect. But some cities in the world are very clean because conscious people are very good.