Undercity, Megropolis One

The undercity was an area beneath Megropolis One on Pluto. Its only inhabitants were outlaws who had escaped from the Company's society above ground.

There was no lighting in the undercity save for that given by candles, nor where conditions favourable, with much of the surface being covered in filth.

Mandrel was the leader of the outlaws living in the undercity. They were forced into the city whenever they wanted food as they had no source themselves. Many of those above ground had heard of the undercity and those that lived there, but knew little detail.

After he was unable to pay his taxes any longer, Cordo headed for the undercity. The Fourth Doctor and Leela joined him. Upon arrival, Mandrel told them that they could stay if the Doctor delivered a consumcard to the Consum Bank on subway 37. However, Mandrel threatened him, saying he had to return before a set time or Leela would be killed. Cordo went with the Doctor to show him the way.

Cordo made his way back to the undercity after some time and reported that the Doctor had been captured. At this news, Leela and Cordo left to rescue him. The Doctor returned on his own some time later, having been freed. Mandrel did not believe this story and so readied a hot iron with which to torture him. A friend of the Doctor's, Bisham, used a balcony above the undercity's main level to threaten him into surrender. Mandrel then agreed to help the Doctor take over Main Control while the rest of the outlaws stirred up rebellion among the workers. This left the undercity abandoned. (DW: The Sun Makers)

Other uses
The term "undercity" had previously been used to denote the populated areas of Earth's surface in the 30th century, as opposed to the Overcities. (NA: Original Sin)