Dungeons/Levels that take place inside a much larger organism

1 - Inside Jabu-Jabu’s Belly (The Legend of Zelda: Ocarina of Time) - The game’s third dungeon is the insides of a massive fish.

2 - The Bonehemoth (Fossil Fighters Champions) - During a trip to Icegrip Plateau, the second of Illium Island’s Dig Sites, the player, their allies and the BareBones Brigade Executives are all devoured by a giant whale known as the Bonehemoth. The whale’s insides are a fully-functional Dig Site you can actually return to at any time after escaping; Robinson tricks the Bonehemoth into swallowing a teleporter, which makes it possible for you to return to the area whenever you want.

3 - Lord of the Underworld (Kid Icarus: Uprising) - The 23rd chapter of the game sees Pit finally facing off against Hades, after numerous chapters of fighting other threats, such as Viridi, the Aurum and the Chaos Kin. However, Hades is able to destroy the Three Sacred Treasures, and not long after, inhale Pit. Thus, the chapter’s ground sequence takes place in Hades’ innards, and concludes with the infamous boss fight against his heart.

4 - Gardenia (Tales of Hearts) - The final dungeon of this game is essentially the insides of a planet-sized alien bioweapon. Gardens is a Xerom created by the main villain to manipulate the souls of his fellow Minerans in the hopes the endless wars plaguing his homeland would finally end. However, the plan went horribly wrong; Gardenia instead devoured the Spiria (Souls) of every single Mineran on the planet, leaving only Creed, his implied-lover Fluora, and Fluora’s sister Lithia, alive. And Fluora dove inside Gardenia to hold it back from the inside. Thus, Creed spent 2,000 years hopping from Organican vessel to Organican vessel, trying to resurrect Gardenia both to save Fluora and to harvest all of Organica’s souls to revive the people he accidentally got killed.