Istanbul, the capital city of Turkey, lies on the Bosphorus Strait, at the border between Europe and Asia. Due to its strategic location Istanbul has been of great significance for several centuries and has often been fought over between regional powers.

A "megacity" is an urban or metropolitan area which has a population over 10 million people. 

Here are the populations of the cities from this question: 

Tokyo: 37,900,000

Seoul: 26,100,000

Shanghai: 25,400,000

Jerusalem: 809,112

London: 8,540,000

Tokyo is currently the most populated city today. Jerusalem does not even reach 1 million so it can not be classified as a megacity. 

Jerusalem, Israel is not a Megacity. It only has a population of about 800,000. Though it is a very important city in the world, as it is often fought over and boasts a significant historic site of three of the major world religions (Judaism, Christianity, and Islam). It's population is not currently growing, probably due to violence and war as well as the religious focus of the city rather than economic growth.

Tokyo, Japan is a Megacity and is the most populated city in the world, boasting a population of 38 million.

New York, USA is a Megacity and was one of the first two Megacities in the world. The current population of New York is 23 million.

Jakarta, Indonesia is number 3 in the world in population rank, coming in behind Tokyo and Shanghai. Jakarta has a population of 31 million.

Paris, France is one of the smaller Megacities in the world, but nevertheless it is a Megacity. Paris has a population of 12 million.

Many contemporary cities have enacted measures to prevent the continuous urban sprawl that results from their ever-growing populations. They reserve a portion of land for farms, parks, forests, and other such things. This is called a “greenbelt.”

The “metropolitan area” of a city is defined as all the areas surrounding a city that can be said to have a high-level of economic or social integration with the city. So, if the majority of people who live in an area outside of a city’s political limits still commute to the city for work, school, or recreation than that area is said to be within the city’s “metropolitan area.” The definition is based on economic and social integration, NOT on physical proximity.

The term “ghettoization” is used to refer to the degradation of inner cities in America. It occurs when affluent white Americans move out of inner cities to the suburbs and this population is replaced with much poorer populations. It occurred throughout the United States in the twentieth century and is one of the more significant problems facing American cities in the twenty-first century.

The term “megalopolis” is used to describe a stretch of land that contains multiple cities and connecting suburban regions. The stretch of land from Boston to Washington D.C. also includes New York City, Philadelphia, Baltimore, and all the attending suburban areas. It is a highly urbanized stretch of land and therefore it is called a “megalopolis.”

In major American cities, poor urban areas suffer from a variety of problems due to a few specific realities of their geographic locations. Poor inner-city neighborhoods are usually much more densely populated than their wealthier counterparts, but with fewer amenities due to their worse infrastructure. One of the best examples of the problems produced by these issues is the lack of quality food options from high-end grocers, farmers' markets, or specialty stores.

Agglomeration is a real-world marketing ploy in which establishments are located close to one another to help convince like-minded consumers who may walk out of one establishment and want to go to another. For example, coffee shops and sandwich shops tend to be located close to one another with the idea that customers may leave the coffee shop and want a sandwich, or vice versa. 

The Federal Government defines environmental justice as the official government policy that all American citizens deserve to be treated equally with regard to the passage and application of environmental laws— regardless of where they live. This policy emerged out of fear that environmental issues like pollution were disproportionately affecting lower-income communities.