Castelia Gym is a location in the Unova region of the Pokémon series. It is known for its unique design, resembling a skyscraper, and is home to the Bug-type Gym Leader, Burgh. Trainers challenge the gym to earn the Insect Badge. The gym features various puzzles and obstacles that trainers must navigate to reach Burgh. Defeating him in battle allows players to progress in their journey, as well as gain access to new areas and abilities. The gym is a popular destination for trainers seeking to improve their skills and collect badges.