Metropolis in the context of "Megacities"

Mainland is defined as "relating to or forming the main part of a country or continent, not including the islands around it [regardless of status under territorial jurisdiction by an entity]." The term is often politically, economically and/or demographically more significant than politically associated remote territories, such as exclaves or oceanic islands situated outside the continental shelf.

In geography, "mainland" can denote the continental part of any polity or the main island within an island nation. In geopolitics, "mainland" is sometimes used interchangeably with terms like metropole as an antonym to overseas territories. In the sense of "heartland", mainland is the opposite of periphery. In some language a separate concept of "mainland" is missing and is replaced with a "continental portion".

A conurbation is a region consisting of a number of metropolises, cities, large towns, and other urban areas which, through population growth and physical expansion, have merged to form one continuous urban or industrially developed area. In most cases, a conurbation is a polycentric urbanised area in which transportation has developed to link areas. They create a single urban labour market or travel to work area.

Conurbations often emerged in coal-mining regions during the period of the Industrial Revolution.Patrick Geddes coined the term in his book Cities in Evolution (1915). He drew attention to the ability of the new technology at the time of electric power and motorised transport to allow cities to spread and agglomerate together, and gave as examples "Midlandton" in England, the Ruhr in Germany, Randstad in the Netherlands, and the Northeastern Seaboard in the United States.

Greek colonisation refers to the expansion of Archaic Greeks, particularly during the 8th–6th centuries BC, across the Mediterranean Sea and the Black Sea.

The Archaic expansion differed from the Iron Age migrations of the Greek Dark Ages, in that it consisted of organised direction (see oikistes) away from the originating metropolis rather than the simplistic movement of tribes, which characterised the aforementioned earlier migrations. Many colonies, or apoikiai (Greek: ἀποικία, transl. "home away from home"), that were founded during this period eventually evolved into strong Greek city-states, functioning independently of their metropolis.

Rome is the capital city and most populated comune (municipality) of Italy. It is also the administrative centre of the Lazio region and of the Metropolitan City of Rome. A special comune named Roma Capitale with 2,746,984 residents in 1,287.36 km (497.1 sq mi), Rome is the third most populous city in the European Union by population within city limits. The Metropolitan City of Rome Capital, with a population of 4,223,885 residents, is the most populous metropolitan city in Italy. Its metropolitan area is the third-most populous within Italy. Rome is located in the central-western portion of the Italian Peninsula, within Lazio (Latium), along the shores of the Tiber Valley. Vatican City (the smallest country in the world and headquarters of the worldwide Catholic Church under the governance of the Holy See) is an independent country inside the city boundaries of Rome, the only existing example of a country within a city. Rome is often referred to as the City of Seven Hills due to its geography, and also as the "Eternal City". Rome is generally considered to be one of the cradles of Western civilization and Western Christian culture, and the centre of the Catholic Church.

Rome's history spans 28 centuries. While Roman mythology dates the founding of Rome at around 753 BC, the site has been inhabited for much longer, making it a major human settlement for over three millennia and one of the oldest continuously occupied cities in Europe. The city's early population originated from a mix of Latins, Etruscans, and Sabines. Eventually, the city successively became the capital of the Roman Kingdom, the Roman Republic and the Roman Empire, and is regarded by many as the first-ever Imperial city and metropolis. It was first called The Eternal City (Latin: Urbs Aeterna; Italian: La Città Eterna) by the Roman poet Tibullus in the 1st century BC, and the expression was also taken up by Ovid, Virgil, and Livy. Rome is also called Caput Mundi (Capital of the World).

London is the capital and largest city of both England and the United Kingdom, with a population of 9.1 million people in 2024. Its wider metropolitan area is the largest in Western Europe, with a population of 15.1 million. London stands on the River Thames in southeast England, at the head of a 50-mile (80 km) tidal estuary down to the North Sea, and has been a major settlement for nearly 2,000 years. Its ancient core and financial centre, the City of London, was founded by the Romans as Londinium and has retained its medieval boundaries. The City of Westminster, to the west of the City of London, has been the centuries-long host of the national government and parliament. London grew rapidly in the 19th century, becoming the world's largest city at the time. Since the 19th century the name "London" has referred to the metropolis around the City of London, historically split between the counties of Middlesex, Essex, Surrey, Kent and Hertfordshire, which since 1965 has largely comprised the administrative area of Greater London, governed by 33 local authorities and the Greater London Authority.

As one of the world's major global cities, London exerts a strong influence on world art, entertainment, fashion, commerce, finance, education, healthcare, media, science, technology, tourism, transport and communications. London is Europe's largest city economy and one of the world's major financial centres. London hosts Europe's largest concentration of higher education institutions, comprising over 50 universities and colleges and enrolling more than 500,000 students as at 2023. It is home to several of the world's leading academic institutions: Imperial College London, internationally recognised for its excellence in natural and applied sciences, and University College London (UCL), a comprehensive research-intensive university, consistently rank among the top ten globally. Other notable institutions include King's College London (KCL), highly regarded in law, humanities and health sciences; the London School of Economics (LSE), globally prominent in social sciences and economics; and specialised institutions such as the Royal College of Art (RCA), Royal Academy of Music (RAM), the Royal Academy of Dramatic Art (RADA), the School of Oriental and African Studies (SOAS) and London Business School (LBS). It is the most-visited city in Europe and has the world's busiest city airport system. The London Underground is the world's oldest rapid transit system.

Colonies in antiquity were post-Iron Age city-states founded from a mother-city or metropolis rather than from a territory-at-large. Bonds between a colony and its metropolis often remained close, and took specific forms during the period of classical antiquity.Generally, colonies founded by the ancient Phoenicians, Carthage, Rome, Alexander the Great and his successors remained tied to their metropolis, though Greek colonies of the Archaic and Classical eras were sovereign and self-governing from their inception. While earlier Greek colonies were often founded to solve social unrest in the mother-city by expelling a part of the population, Hellenistic, Roman, Carthaginian, and Han Chinese colonies served as centres for trade (entrepôts), expansion and empire-building.

A megalopolis (/ˌmɛɡəˈlɒpəlɪs/), also called a supercity or megaregion, is a group of metropolitan areas which are perceived as a continuous urban area through common systems of transport, economy, resources, ecology, and so on. They are integrated enough that coordinating policy is valuable, although the constituent metropolises keep their individual identities. The megalopolis concept has become highly influential as it introduced a new, larger scale thinking about urban patterns and growth.