Sky Land

Sky Land (alternatively The Sky, Cloud Castle , or Sky World ) is the fifth world in Super Mario Bros. 3. Sky Land has nine levels, three Hammer Brothers, two Fortresses, three Toad Houses, three Spade Panels, a king's palace, and a special Tower level. There are two parts to the world, "The Ground" and "The Sky", connected by the Tower level. The first three levels, the first Fortress, the first Toad House, one Spade Panel and two of the Hammer Brothers are on the ground, while everything else is in the sky. The world's Airship can move between the two.

The Koopaling Roy Koopa presides over Sky Land. The real king of Sky Land is an older man, wearing a crown, and with long white hair, and a long white beard. During the events of the game, the Koopalings turn him into a vulture; the SNES and Game Boy Advance versions of Super Mario Bros. 3 see him get turned into an Albatoss.

The Super Mario Advance 4: Super Mario Bros. 3 map shows that the ground area of Sky Land was located to the east of Giant Land, and south of Dark Land.

Hammer Brothers
Two sets of Hammer Bros. will move around the land portion of the map, with one set of Hammer Bros. moving around in the sky. The arenas are similar between them, with two rows of seven Brick Blocks, though the area they are fought in differs by location. The first Hammer Bro. set will reward the player with a P-Wing upon being defeat, the second will reward a Super Star, and the third will reward a Music Box. If the player meets the prerequisites for the Treasure Ship, a Hammer Bro will turn into the ship.

The Adventures of Super Mario Bros. 3
Sky Land appeared in several episodes of The Adventures of Super Mario Bros. 3. The ground portion of Sky Land never made an appearance; Sky Land was implied to exist directly above the Mushroom Kingdom itself, and is connected to the mainland by a stairway made out of floating blocks. Sky Land is ruled by Emperor Ed.

Reign Storm: One of the problems that Mario and Luigi face while trying to run the Mushroom Kingdom during Princess Toadstool's absence is that the stairway to Sky Land is floating off and dropping people in the garbage dump.

A Toadally Magical Adventure: While unstated, the Ace Magic Wand Factory seems to be based in Sky Land. Bowser and several Koopalings have their sights set on obtaining a special wand that is being delivered to the Wizard King of the West; having spotted the Koopas, the Wizard King of the West alerts the Mario Bros. and requests for them to prevent the wand from being stolen.

Up, Up, and a Koopa: After abducting Emperor Ed, Bowser uses Kooky's new Kooper-Dooper Raiser-Upper from onboard the Doom Ship to levitate everything in the Mushroom Kingdom up to Sky Land (sometimes called "Sky World" in this episode) in an attempt to force Princess Toadstool into surrendering her kingdom. However, Bowser overloads the Raiser-Upper causing everything that was being levitated to fall back down to the Mushroom Kingdom. In the process, Emeperor Ed falls out of the Doom Ship and lands on Toad. He alerts Princess Toadstool as to what's going on, so Mario and Luigi obtain Raccoon Power to bring Emperor Ed back to Sky Land and fly to the Doom Ship. However, they get caught, prompting Princess Toadstool and Toad to fly up to Sky Land using P-Wings. Bowser then decides to take over Sky Land as well by tormenting its people with the Raiser Upper. However, Princess Toadstool and Toad make it to the Doom Ship, where they rescue Mario and Luigi. The group steals the Raiser Upper and use it to not only restore Sky Land and the Mushroom Kingdom back to normal, but to levitate the Doom Ship back to Dark Land.

Trivia

 * There is a glitch in the original NES version of the game in which the Airship can "hide" in an undetermined area between "The Ground" and "The Sky". This means that, if this happens, the player can be permanently stuck and unable to continue, as they cannot reach the Airship to challenge it. The Airship appears to be in the top left corner of Sky Land's screen, where a miniature version of the ground is visible.
 * The ground map on the NES and SNES versions has a different layout when seen on the map on "The Sky"; there more turns in the path in the actual game, and it shows a path Mario cannot take going north from the Tower. This was fixed in the GBA version.
 * The map icon for the fortress is given a blue coloring for the sky portion of this world. This doesn't happen anywhere else in the game.
 * The tower that takes Mario/Luigi to the sky portion of the game resembles Mount Purgatory from Dante Alighieri's Divine Comedy; the mountain also leads to heaven, just as the tower leads to the sky.
 * Princess Peach's Final Smash in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U uses a sped-up remix of the theme that plays in the sky portion.