The Dalek City was the home of the Daleks on Skaro.
History
At the time of the First Doctor's visit to the planet, the city dated back from before the Thousand Year War. The Daleks lived not in the city itself, but rather below it where they thought they were shielded from radiation.
The entire city ran on static electricity transmitted through metal floors, which the Daleks of this era of Skaro history required to power their casings. As a consequence of this dependence, the Daleks were unable to leave their city. They were unaware that a group of Thals had also survived the neutronic war.
The city at one side had a natural protection in the form of the Lake of Mutations. Near the swamp was a lake where the Daleks got their water.
After the Daleks were destroyed, the Thals moved into the City. (TV: The Daleks)
During the war between the Humanised Daleks and the Daleks ruled by the Emperor Dalek, the Daleks had a city which the Second Doctor, having visited before, knew how to navigate. Fighting between the two groups of Daleks devastated the city ending the Great War. (TV: The Evil of the Daleks, PROSE: The Evil of the Daleks)
After the Civil War, the Daleks rebuilt the Dalek City and introduced a new command structure involving Gold Daleks which outranked the Black Daleks. (TV: Day of the Daleks, TV: Frontier in Space, PROSE: Day of the Daleks)
Following the Imperial-Renegade Dalek Civil War, the Dalek Prime controlled the Dalek city and it had a spaceport. A brief but destructive war began on the city. (PROSE: War of the Daleks)
After the Cult of Skaro was formed, they headed on the secret Strategy Chambers of the Cult of Skaro. a special area of the city away from other Daleks. (PROSE: Birth of a Legend)
The Dalek City appeared on a rebuilt Skaro to house the dying Davros. (TV: The Magician's Apprentice) The city, along with the Daleks loyal to Davros, was destroyed by the sewer Daleks when they were rejuvenated by the Twelfth Doctor's regeneration energy and revolted against those who had discarded them. (TV: The Witch's Familiar)
Behind the scenes
The Dalek Handbook states that the city was named Kaalann. Dialogue in the video game City of the Daleks suggests that this city is the same as the Kaalann in the game, when the Eleventh Doctor says of Kaalann, "Last time I saw it, it was in ruins and the Daleks had fled".
The Target novelisation of Remembrance of the Daleks states that the Dalek city is called Mensvat Esc-Dalek and is located in the Vekis Nar-Kangji (Plain of Swords).
