Bianco Square is an area of Delfino Plaza that is home to the Grand Pianta Statue in Super Mario Sunshine. Its name likely originates from the fact that the Rainbow M entrance to Bianco Hills is located on the front of the Grand Pianta Statue, which is found directly in the center of the square. It is one of the main areas of Delfino Plaza and is also one of the most open areas in the plaza. It is first seen in the opening cutscene where the Piantas greet those on the Toad Express. As the game progresses, all three of FLUDD's nozzles (the Hover Nozzle, the Rocket Nozzle, and the Turbo Nozzle) appear here, positioned directly behind the Grand Pianta Statue. When starting the game after quitting previously, Mario usually appears in Bianco Square. In addition, Bianco Square also provides direct access to several major levels, including Bianco Hills, Ricco Harbor, and Sirena Beach, as well as providing access to Yoshi (once unlocked) and a few hidden Shine Sprites.
It is also the first area that Mario is ordered to clean the goop off of (Delfino Airstrip having already been cleaned prior). When Mario first enters the square, he is confronted with a large mass of goop shaped like an octopus, called a Generator. In the center of it lies a Gatekeeper. After he successfully sprays and defeats the Gatekeeper, the goop disappears, and the Grand Pianta Statue reappears, triggering the first major event of the game. Shadow Mario jumps down from atop the Grand Pianta Statue, and proceeds to kidnap Princess Peach. Mario successfully stops him, and Shadow Mario runs back to Bianco Square, where he paints the Color Portal to Bianco Hills on the front of the Grand Pianta Statue's base.