A pounla (plural: plounla) was a type of city built by the Orion civilization, which was constructed underground.
The Orion Colony world of Tini was home to 5922 plounla, each with a population of over one billion people who lived in a large warren-like environment. They were fed by evaporator farms that ringed each pounla and relied on life support systems. From these cities, Orions conducted mining operations. Many other Orions found it difficult to live in such conditions. (FASA RPG module: The Orions: Book of Common Knowledge)