The Last Great Time War between the Time Lords and the Daleks devastated the city. It lay in ruins and Varga plants had invaded the structure. The Doctor and Amy explored Kaalann's many different areas in the city while looking for the device that the New Paradigm Daleks were using to alter the timeline.
The Doctor and Amy visited here after travelling through the Eye of Time from an alternative timeline back to this time, from an alternative future version of the city which the Daleks had rebuilt. The Doctor managed to deactivate the Eye, returning the timeline to normal. Kaalann was also returned to normal and reverted to its ruined state. (GAME: City of the Daleks)
Kaalann had several storerooms with discarded Dalek parts. It was in one of these that the Doctor landed his TARDIS.
Kaalann was used by the New Dalek Paradigm as a giant factory. Daleks were produced on a production line. This area was of higher security; it was heavily guarded by Drone and Scientist Daleks. The factories were connected to the other rooms by corridors infested with Varga plants.
The Visualiser room was a large room where the Daleks recorded and monitored all Dalek activity across the universe. It was controlled by the Visualiser Eye, a giant "Librarian Dalek" on one of the walls. The room was full of large data banks and also contained three consoles. The Doctor had to use these consoles to deactivate the Eye's security beam.
Supreme Council Chamber
The Supreme Council Chamber was where the Dalek Emperor and the Eye of Time were located. The chamber had two levels. The Emperor and the Eye were located on the top level. It was in this room that the Doctor deactivated the Eye and reversed the timeline. (GAME: City of the Daleks)
Kaalann's atmosphere was heavily polluted by the Daleks' factories. Thirty percent of the atmosphere in the area was made up of sulphuric acid. The sky had an orange colouration and acid rain constantly fell over the city.
Behind the scenes
It remains unclear as to whether to identify Kaalann as the Dalek City seen in previous stories. Doctor Who: The Dalek Handbook asserts this but also speculates as to the existence of multiple alternative timelines.