Title: List of largest cities
Content:  The United Nations uses three definitions for what constitutes a city, as not all cities in all jurisdictions are classified using the same criteria. Cities may be defined as the cities proper, the extent of their urban area, or their metropolitan regions. The largest city by population using the city proper definition, which is the area under the administrative boundaries of a local government, is Chongqing, China. The largest city by population using the metropolitan area definition, which is a loose term referring to urban area and its primary commuter areas, is Tokyo, Japan. The largest city by population using the urban area definition, which is a loose term referring to a contiguous area with a certain population density, is also Tokyo, Japan.
Title: List of largest cities throughout history
Content:  This article lists the largest human settlement in the world (by population) over time, as estimated by historians, from 7000 BCE when the largest populated place in the world was a proto-city in the Ancient Near East with a population of about 1,000–2,000 people, to the year 2000 when the largest urban area was Tokyo with 26 million. Alexandria, Rome, or Baghdad may have been the first city to have 1,000,000 people, as early as 100 BCE or as late as 925 AD. They were later surpassed by Constantinople, Chang'an, Hangzhou, Jinling, Beijing, London (the first city to reach 2 million), and New York (the first to top 10 million), among others, before Tokyo took the crown in the mid-20th century. As of 2020, the Greater Tokyo Area is the most populous metropolitan area in the world, with more than 37.393 million residents. Many of the figures are uncertain, especially in ancient times. Estimating population sizes before censuses were conducted is a difficult task.
Title: Europe
Content:  The four largest urban areas of Europe are Istanbul, Moscow, London and Paris. All have over 10 million residents, and as such have been described as megacities. While Istanbul has the highest total city population, it lies partly in Asia, making Moscow the largest city entirely in Europe. The next largest cities in order of population are Saint Petersburg, Madrid, Berlin and Rome, each having over 3 million residents. When considering the commuter belts or metropolitan areas, within the EU (for which comparable data is available) Moscow covers the largest population, followed in order by Istanbul, London, Paris, Madrid, Milan, Ruhr Area, Saint Petersburg, Rhein-Süd, Barcelona and Berlin.
Title: North America
Content:  pop./km2 (0.067 pop./mi2). While the United States, Canada, and Mexico maintain the largest populations, large city populations are not restricted to those nations. There are also large cities in the Caribbean. The largest cities in North America, by far, are Mexico City and New York. These cities are the only cities on the continent to exceed eight million, and two of three in the Americas. Next in size are Los Angeles, Toronto, Chicago, Havana, Santo Domingo, and Montreal. Cities in the sun belt regions of the United States, such as those in Southern California and Houston, Phoenix, Miami, Atlanta, and Las Vegas, are experiencing rapid growth. These causes included 
Title: Americas
Content:  urban area, but also satellite cities plus intervening rural land that is socio-economically connected to the urban core city, typically by employment ties through commuting, with the urban core city being the primary labor market. There are three urban centers that each hold titles for being the largest population area based on the three main demographic concepts: In accordance with these definitions, the three largest population centers in the Americas are: Mexico City, anchor to the largest metropolitan area in the Americas; New York City, anchor to the largest urban area in the Americas; and São Paulo, the largest city proper in the Americas. All three cities maintain Alpha classification and large scale influence.
Title: Metropolis
Content:  In Kazakhstan, Almaty is the largest city whilst the capital Nur-Sultan is the second largest, Shymkent is the third largest city, all three having populations of over one million each.
Title: List of cities in the Americas by population
Content:  Italics represents capital city Bold represents largest city in country
Title: Istanbul
Content:  Throughout most of its history, Istanbul has ranked among the largest cities in the world. By 500 CE, Constantinople had somewhere between 400,000 and 500,000 people, edging out its predecessor, Rome, for the world's largest city. Constantinople jostled with other major historical cities, such as Baghdad, Chang'an, Kaifeng and Merv for the position of the world's largest city until the 12th century. It never returned to being the world's largest, but remained the largest city in Europe from 1500 to 1750, when it was surpassed by London. The Turkish Statistical Institute estimates that the population of Istanbul Metropolitan Municipality was 15,519,267 at the end of 2019, hosting 19 percent of the country's population. 64.4% of the residents live 
Title: Indigenous peoples of the Americas
Content:  the largest cities in the world, Tenochtitlan (the historical site of what would become Mexico City), with an estimated population of 200,000 for the city proper and a population of close to five million for the extended empire. By comparison, the largest European cities in the 16th century were Constantinople and Paris with 300,000 and 200,000 inhabitants respectively. The population in London, Madrid and Rome hardly exceeded 50,000 people. In 1523, right around the time of the Spanish conquest, the entire population in the country of England was just under three million people. This fact speaks to the level of sophistication, agriculture, governmental procedure 
Title: 1153
Content: Estimation: Constantinople, capital of the Byzantine Empire, becomes the largest city of the world, taking the lead from Merv in the Seljuk Empire. 

Question: three largest cities in the world by population?
Answer: Beijing.
Shanghai.
Delhi.