Brobdingnag is a large continent that acts as the "island" nation of the Brobdingnagians, a giant race of humanoids who are of truly titanic size. Everything on Brobdingnag is gigantic, including the plants, animals, food, buildings and etc, befitting of the giants that make it their home. Brobdingnag was one of the many locations visited by Gulliver during his travels.
In the 1977 film, Gulliver does not go to Brobdingnag until the very end of the film, where he encounters a giant, however the movie ends there and none of Brobdingnag is seen.
In the 1996 mini-series, the entire affair at Brobdingnag is loudly conveyed within an insane asylum by Gulliver while all the patients stare at him in deranged amusement. As in the book, he mentions that he landed on Brobdingnag shortly after leaving Lilliput on a small raft. There he is abducted by a giant villager and after several events he is able to meet the queen of Brobdingnag. After thinking that their society is too different from English society, he decides to introduce gunpowder to the giants in hopes that it will make them become more like Englishmen, instead the giants are appalled by the dangerous substance and consider English society to be barbaric.
In the 2010 film, Gulliver (played by Jack Black) is banished to the island beyond the fog by Blefuscun conquered Lilliput army. The island beyond the fog, while not named (only named in the credits) is none other than Brobdingnag, however only one giant little girl is seen who lives in a large house near the beach. The rest of Brobdingnag and its kingdom is not seen or mentioned.