As name implies, that castle was King K. Rool's residence infested by Kremling Krew guards that protect. In peak where have K. Rool's heads sculpture below of castle is completely frozen with ice caverns and constantly battered by high winds inside mine. Inside the castle is full chains, torches and treacherous traps kept; these traps includes: moving soil, bottom and toxic waste. This keep must have been build when K. Rool has became leader of island.
During the events of the second game, Diddy and Dixie defeat number of Kremling Krew crooks by invades this fortress where DK was prisoner. Upon arriving at the tower where Donkey Kong was imprisoned, K. Rool escape with him in his aerial gunship. After of final battle in Lost World, that castle blow up making Crocodile Isle remains be swallowed by sea.
This world does not have a world boss in its final area Stronghold Showdown and is the only world without a boss (except for in the Game Boy Advance re-release where Kerozene is the world boss in said area).
Donkey Kong Island can be seen from this world map, but not in the Game Boy Advance remake.