Ricco Tower

From the Super Mario Wiki

Ricco Tower is a place in the game Super Mario Sunshine. It is located in Ricco Harbor and is surrounded by girders and Wind Duppys. In every Episode except Episode 4, the tower's entry way is blocked by metal bars. When Mario enters the tower Shadow Mario steals FLUDD and a secret level begins. The secret level contains long spinning blocks moving gears and, like all secret levels, two 1-Up Mushrooms. It is unknown what the tower's purpose is.

Ricco Tower made a minor appearance in Mario Power Tennis in the Ricco Harbor Court.