Ozai's airship base

This airship base is located on a remote and hidden Fire Nation inhabited island, within striking distance of the Earth Kingdom. The Fire Nation has been building a fleet of airships at this base in preparation for the day of the comet. Toph, Suki and Sokka manage to arrive at this location via Giant Eel Hound just as the airships take off. They sneak into one of them with Toph's Earthbending and proceed to sabotage Ozai's plan to burn down the Earth Kingdom.