City

A city is a type of settlement that sapient species create. They were often large and complex. Cities can be built on planets or on Space stations. Exact elements of cities depend on the species that create them.

The word "urban" is often used to describe city areas.

Human
For a list of human cities, see here here
 * Ancient humanity - Prior to the activation of the Halo Array, one of humanity's greatest cities was Marontik.


 * Post-Halo activation humanity - Human cities can be found near water bodies  or almost totally land locked. Cities have been built in deserts, in mountainous valleys, along rocky coastlines, and on islands.


 * Some cities are filled with buildings. Occasionally buildings have landing pads for various aerospace craft, skybridges connecting to other buildings and outdoor courtyards on roofs. Other cities are actually arcologies. Several examples of this include the Castra Arcology, the Haven arcology. and New Mombasa. In different cases, the city contains minimal or no buildings at all like the  which became the hub of a city composed of permanently parked starships.


 * In terms of physical infrastructure, cities often have transit systems featuring Maglev trains. Roads for Civilian vehicles were also a common feature of human cities. Quite a few cities also prominently hosted Space elevators. Paired with the space elevator, all six of Earth's tether cities have Superintendent-class artificial intelligences.


 * Structures and physical infrastructure were created using metals, concrete-like materials, and wood-like materials.


 * Cities often have their own organizations like emergency forces. Examples of emergency services include the New Mombasa Police Department, Boston Emergency, or Elysium City Law Enforcement. A select number of cities are considered "capitals". Some like Casbah City are their planet's capital. Others like Cairo were the capital of their country.

Species of the Covenant

 * Covenant - Designed as the Covenant's capital, High Charity featured its own city. The Covenant were also known to use derelict Forerunner cities, like with the Ten Cities of Edification.


 * Kig-Yar - The Kig-Yar had developed at least one major city, Tilu City. It was old and primarily filled with merchants.

Forerunner
Forerunners built their own cities. There were quite a few different types of cities.

The capital of the Ecumene was the city-station of Maethrillian.

Forerunners also built cities on planets, some of which survived the nearly 100,000 year gap from the firing of the Halo Array like the Ten Cities of Edification. Other ground cities of the Forerunners were the ones built on Triniel.