Grass Land

Grass Land is the first world of Super Mario Bros. 3. It has six levels, one Hammer Bro. to encounter, one fortress, two Toad Houses, and a castle that has been taken over by an Airship. In level three and in the fortress Mario can get two out of the three Warp Whistles in the game. Using both of them lets him take a shortcut to World 8, Dark Land. Larry Koopa (the youngest Koopaling) guards this area and is the boss of Grass Land.

The king was transformed into a dog in the original NES version. However, in the Super Mario All-Stars remake for the SNES he was turned into a cobrat.

1-1
Mario begins his Koopa-Kickin', Goomba-Stompin', Mushroom Kingdom quest on this level. If able to get a Super Leaf, on the stretch with the Goombas, Mario can uncover a secret by running along, jumping at the end of the stretch, and rapidly pressing the A Button to get to a cloud-top cache! Also, if enough momentum is gathered, Mario can lead off the edge of the long cloud platform and fly to a high-up pipe, where coins making a number 3 design are found! Also at the beginning of the level should see a tall white block, stand on the top and hold down on the d-pad and Mario will go behind the foreground.

1-2
Goombas have infested the rolling green hills of the Mushroom Kingdom. Mario must defeat the vile creatures in order to survive! In the area with a Paragoomba and Goombas pouring out of a high pipe, Raccoon Mario can earn 1-Ups by stomping one, super jumping off it, slowly ascending, and hitting them again and again. Also, a P-Switch under a Venus Fire Trap's lair turns Coins into blocks, giving Mario access to a the pipe overhead containing a cache of even more coins! Also, the many Note Blocks can contain secrets.

1-3
In this level Mario can gain access to a Coin Heaven. On the big block formation in the very first part (after the Boomerang Bro.), if the Koopa Troopa on the top is hit to the left, it will begin to rapidly rebound, destroying many of the blocks and eventually falling out. Mario must go to the block stack on the left, stand against it, and jump to reveal a hidden Pink Note Block, that will allow him to get into Coin Heaven if he jumps on it. The player will then find some Wood Blocks, one of them containing a Leaf if Mario bumps into one. A Goomba and a Paragoomba can be seen here, along with another Boomerang Bro.. The player will now see a red Koopa Troopa on top of a white block. If the player ducks under the white block for five seconds, and runs behind the black background, they will be inside a hidden Toad House, which has only one Treasure Box in it containing a Warp Whistle. The player can also keep going past the white block and a Paragoomba to reach the Roulette Box of the level.

1-4
Gold Coins and 1-Ups abound on a challenging stage of leaps and bounds. If all Coins in the level are collected, a White Toad House will appear, which has a P-Wing inside!

World 1 Fortress
A brown Koopa boss named Boom Boom defends Grass Land's stony Fortress in this level. The second Warp Whistle can be achieved by going through the entire Fortress to a door with a Dry Bones nearby; Raccoon Mario can then race back and forth on the stretch of floor by the door, eventually lifting off and going up and onto a platform high above the door and partially off the screen. When Mario gets to the end of this platform, he should press Up on the D-Pad to enter into a secret door with the Warp Whistle.

To defeat Boom Boom, the player must jump on him three times successfully damaging him, or by throwing several fireballs at him. If Boom Boom is covered in spikes, than the player should not jump on him, or else the player will take damage. When Boom Boom is defeated, he leaves behind an orb marked with a ?. When the player picks this up, a nearby locked door with disappear.

1-5
In this level, the player must delve into a dark cavern and face all kinds of unfriendly cave-dwellers. Another entrance to a Coin Heaven can be found by taking the upper route after the two Piranha Plants, then jumping against the left wall to "expose another" red Note Block!

1-6
This level isn't much different from what's been seen so far. The player must jump along platforms over gaps in order to survive. Along the way, the player can collect many coins earning the chance for a 1-Up as well as a higher score.

Larry's Airship
In this level the player must board Larry Koopa's airship. It is overflowing with cannons for an additional challenge. The player must dodge obstacles and jump over gaps, finally reaching a silver pipe in order to get to Larry Koopa. Larry's only attack is to use the magic wand to shoot rings at Mario (or Luigi). The player must dodge the rings and stomp Larry thrice (or throw several fireballs at him) in order to win the wand back. The king of this world will then change back from a dog (NES version) or a Cobrat (GBA remake) into his normal self.

Trivia

 * In Yoshi's Safari Grass Land reappears as the first level in Jewelry Land.
 * A rendition of the theme for Grass Land is played on the Level Up Option Screen in the game Paper Mario. The same applies to the Minigame Selection screen in Super Mario 64 DS.
 * This is the only World of Super Mario Bros. 3 that does not have an alternate name.