A Forum was a public square in a Roman municipium, or any civitas, reserved primarily for the vending of goods; i.e., a marketplace, along with the buildings used for shops and the stoas used for open stalls. In addition to its standard function as a marketplace, a forum was a gathering place of great social significance, and often the scene of diverse activities, including political discussions and debates.
The Griffin Family tours a forum while in Italy in "Boopa-Dee Bappa-Dee". While Lois tries to teach the kids some of the history, Peter is being a spoilsport and introduces them to the Penthouse forum. Given a choice, the kids prefer to hear Peter's story of a girl that moves to New York without any underpants.