Manhole

Manholes are located in various places in Super Mario Sunshine with most of them being found in Delfino Plaza. Manholes lead to the underground sewer system that can lead Mario to secret areas or find collectibles like coins. To access a manhole, Mario has to Ground Pound it, causing the manhole's Sun design to flip to a moon. They can be seen in the Delfino Plaza stage from Super Smash Bros. Brawl.