Manhole

Manholes, or manhole covers, are covered holes that are located in various places in Super Mario Sunshine. The majority are found in Delfino Plaza, while a few are located in Ricco Harbor. Manholes lead to the intricate underground sewer system, and can lead Mario to places he cannot access aboveground, as well as to coins and other items. To access it, Mario must Ground Pound while over a manhole. The manhole covers, which have a sun on them originally, flip when Ground Pounded, revealing a moon on a green background. When underground, a remix of the underground theme from Super Mario Bros. plays. To get out of a manhole, Mario must jump below a manhole cover. When Delfino Plaza gets flooded, the manholes are replaced with simple textures of them that do nothing; also during this time, one can be seen in the jail cell.

In other games, they are used by Rocky Wrenches as shelter. They can also be found in World 2-3 of New Super Mario Bros.

Manhole covers can also be seen in the Delfino Plaza stage in Super Smash Bros. Brawl, though they serve no purpose.

Manholes also appear throughout the Metro Kingdom in Super Mario Odyssey. Two of them can be captured and moved by Mario, allowing him to fall through the entrance the manhole was blocking. The small one covers an entrance to the Rotating Maze secret area, while the larger, green one covers the entrance to the Underground Power Plant, although the manhole itself is blocked by a parked taxi until Mario finds all four musicians for the New Donk City Festival band performance.

Manholes appear in all four New York Minute courses in Mario Kart Tour on top of Water Geysers. Drivers can perform tricks off of them when the Water Geyser is about to erupt.

Trivia

 * Although Manholes are not seen in Noki Bay, the underground theme is also played when Mario walks through hidden tunnels inside the cliffs.
 * When Delfino Plaza gets flooded, a manhole cover appears inside the jail where a blue coin is found. It is not present during any other point in the game, and it is otherwise unusable. Like the ones outside during the flood, it is merely textured onto the ground instead of fully modeled, so Ground Pounding it via glitches will not do anything.