The Iceberg Lounge is the Penguin's base of operations and the hippest night-club in Gotham. Oswald Cobblepot opened it after he gave up his life of crime, but often only uses it as an excuse against Batman to cover up most of his illegal activities.
The staff consists of the Penguin Himself, and his three co-horts; Jay, Lark and Raven, who usually act as waitresses when business goes smoothly, but often double as Cobblepot's henchmen if another super-criminal becomes too hostile, or if Batman drops by... which he does in almost all of the Lounge's appearances.
The layout of the iceberg is fairly simple... It has a baby-blue antarctic theme complete with a bar, dining area, a giant swimming pool in the middle of the club with a crystal iceberg statue in the center, and several hidden rooms along with the Penguin's office and an armory in the back, according to the storyline Gotham Underground. Oswald even has his own personal dining area upstairs in the lounge, where he can monitor over the entire club.
Almost all of it's customers are either Arkham inmates or just scattered members of organized mobs. Only a select few "citizens" Have dared to enter the lounge, like a nameless couple who had dinner there, who had the misfortune of sitting in the Joker's favorite seat, which lead to their demise. (It was later realized the Joker doesn't really have a favorite seat.) The Riddler is also a well-known customer of the lounge, mainly to the bar, but has lead on to be a very close friend to Penguin, also heavily noted in Gotham Underground. It was once even revealed that Penguin had willed the lounge to Riddler in the event of his death. Several other blue-collar criminals hang there as well, such as Two-Face, The Scarecrow, Mad Hatter, and Hugo Strange.