Underworld

Underworld was the location beneath Bartertown that acted as its power source, keeping the town energized. It is a large underground complex that is a conversion between a pig farm and a power plant, being fueled by the methane produced from pig feces. Human workers are tasked in Underworld to nurture the pigs and provide maintenance for the factory under the supervision of Master Blaster, with Master being the sole individual with the knowledge to operate Underworld and capable of turning it and by extent Bartertown on and off at any moment.

Trivia[]

There were a total of 600 pigs in Underworld. Fearing that buying that many could hurt the pork market, the film crew decided to rent the pigs from a pig farm.
Ironically, George Miller would go on to direct the 1995 film Babe, which starred a pig.