A city was a large settlement.

The Doctor visited many cities across their various incarnations, including Byzantium, (PROSE: Byzantium!) New Byzantium, (PROSE: Shadowmind) New York City, (TV: The Angels Take Manhattan) Tenochtitlan, (PROSE: The Left-Handed Hummingbird) Valhalla, (AUDIO: Valhalla) and Venta Icenorum. (AUDIO: The Wrath of the Iceni) Petronella Osgood noted that the Doctor often visited the city of London. (TV: The Zygon Inversion)

Gallifrey had two major cities, the Capitol and Arcadia. (PROSE: A Brief History of Time Lords) Both were greatly damaged on the last day of the Last Great Time War. (TV: The Day of the Doctor) Other Gallifreyan cities included Trigovia, Olyesti and Slothe. (AUDIO: The Conscript, PROSE: The Infinity Doctors, Blind Fury)

During Skaro's Thousand Year War, the Thals and Kaleds lived in gigantic domed cities, the Thal Dome and Kaled Dome respectively. (TV: Genesis of the Daleks) In the war's aftermath, the first generation of Daleks had built themselves a city. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) 500 years after its construction, the city was invaded by the Thals who disabled its primary source of power. (TV: The Daleks) Spared its city's demise, the Dalek Supreme conspired to rebuild the city and the Dalek race only for Ian Chesterton to destroy the Dalek City by overloading its power feeds. (AUDIO: Return to Skaro) However, the Daleks survived this defeat and would go to rebuild and inhabit their city, a series of events that would be repeated multiple times across history. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) When a Dalek force had believed that they had conquered Alvega, they began construction of a city only for the planet to quite literally turn against them, collapsing their settlement. (COMIC: The Amaryll Challenge)

Using Dalek technology, the victorious Thals had built their own city after the Thal-Dalek battle. (AUDIO: Return to Skaro)

When the Time Lords and the Dalek Empire had fallen following the Last Great Time War, the Unon harvested the technology of both to construct the Perpetual City from which they sought to become the new custodians of time. (COMIC: Weapons of Past Destruction)

Heavily industrialised planets, such as Nomicae, were near completely covered by city infrastructure. (COMIC: The Bidding War)

When the Voord heard the Question, they feared that the Time Lords would return and revert the universe to its pre-Time War state. Harvesting discarded Dalek technology, they shifted their city into a pocket universe to hide themselves. When they were forced to revert themselves to their pre-Time War state, their city was likewise reverted. (COMIC: Four Doctors)

In Earth's 30th century, the wealthy lived in overcities, also called sky cities, city sized platforms that hovered over the ruined surface of Earth where the poor lived. (TV: The Mutants, PROSE: Original Sin) To aid in their colonisation of other planets, the Earth Empire had constructed the Mechanoids to build settlements on selected planets. The Mechanoids built a city on the planet Mechanus only for a series of interstellar wars to end the Empire's expansionist era, leaving the Mechanoids to develop on their own. (PROSE: The Chase)

The Great City of the Exxilons was considered one of 700 Wonders of the Universe. (PROSE: Death to the Daleks)

During the period of their history in which they colonised other planets, the CyberMondans erected Cyber-Cities. (COMIC: Flower Power, The Cyber Empire)

Governments had their main seats of power in a nation or planet's capital city. (TV: The Deadly Assassin, The Sound of Drums, The Return of Doctor Mysterio)

Before it was abandoned, Cui Palta was voted the most beautiful city in the galaxy three years in a row. (PROSE: Clara and the Maze of Cui Palta ^[+]Error: Code 2 - no data stored in variables, cache or SMW.)