World 7-1 (Super Mario Bros. 3)

World 7-1 is the first level of Pipe Land in Super Mario Bros. 3. It is immediately accessible after the player has cleared Ice Land and its own completion unlocks World 7-2.

Layout
Unlike most other levels, this level has the player climb up vertical platforms and the player can "wrap" around the stage, meaning if they move of the left side, they will appear on the right and vice versa.

The player starts in an outside area, with the door to the right leading into the actual level. The player will appear at the bottom of the level and has to jump up some narrow platforms to reach one of two hanging Warp Pipes leading upward. The player then has to avoid Piranha Plants as they try to enter the next hanging pipe, which will take the player upward and to the right. Here, if the player manages to jump around the ? Blocks or fly up using a Super Leaf or similar power-up, they can find a 1-Up Mushroom in a Hidden Block. To continue upward, the player needs to take the Warp Pipe on the left, as taking the Warp Pipe on the right will send the player back downward. On top of the curved pipe is a Koopa Troopa that can be used to hit the grounded ? Blocks and cause a power-up to appear out of the block to the left, and by using a Jump Block to jump onto a floating pipe above, the player can continue upward.

Continuing upward, the player will jump through a pipe that wraps around the stage, which the player can use to build their Power Meter and fly up to the left to reach a pipe leading to a room full of coins. If the player does not have a flight power-up, they will have to jump up pipes to the right, avoiding Piranha Plants and using Jump Blocks to gain additional height. After either path, the player will have to go through a hanging pipe to a small room with Koopa Troopas and a Koopa Paratroopa, the later of which the player can use to reach an invisible block near the Warp Pipe containing a 1-Up Mushroom. Through the Warp Pipe is the goal.

Glitch
The NES version of this level has a "wrong warp" glitch that can allow for arbitrary code execution, typically used by speedrunners to take Mario straight to the scene where Princess Peach is saved at the end of the final castle. With precise timing, Mario can enter from the wrong side of the rightmost Pipe of the bottom two in the main area, causing him to warp downward into glitchy garbage tiles resembling the top of the level. Precise manipulation of various Koopas is used to control what code is executed.

The glitch can also be done in Super Mario All-Stars, but doing it will "properly" wrap Mario around to the top of the level. The glitch cannot be done at all in Super Mario Advance 4. A similar glitch exists on Yoshi's Island 2 in Super Mario World.

Enemies

 * Koopa Troopas
 * Piranha Plants
 * Koopa Paratroopas

Level statistics

 * Power-ups: 1 (Super Mushroom or Super Leaf)
 * 1-Up Mushrooms: 3
 * Secret areas: 0