Nar Shaddaa was very similar to Coruscant, in fact its nickname was "little coruscant," but while Coruscant was dangerous only in the lower levels, Nar Shaddaa was infested with crime and filth on every level. Really, it was an absolutely horrible place. It started out as a legitimate city and major trading center, but became less important as newer trade routes opened up. By about 21,000 ORC, it had been abandoned by the Republic, and was ruled by the Hutts. It became a center for criminal activity. Through the various galactic wars that followed, Nar Shaddaa was occasionally the site of a battle or two. Mostly just crime, though.