A short verticle water level where you need to swim up waterfalls. There is a pipe at the top, which leads to the goal.

Lost Level 2

Game Genie codes:

Underground level that looks very similar to 1-5 towards the end.

Lost Level 3

Game Genie codes:

An extremely short sky level with no goal. Probably a test level due to its shortness, and somewhat different feel compared to other sky levels.

Lost Level 4

Game Genie codes:

A short cloud level, also with no goal. There are underground background tiles at the top.

Lost Level 5

Game Genie code:

The first lost level found: the sinking ice level. It's short, and has a few interesting enemy selections like the flying chain-chomps.

Lost Level 6

Game Genie codes:

This level is half on ground and half underwater. It has a pipe that leads to a different kind of Coin Heaven with not only coins, but also a chest. There's also a goal that can be found if you run through the wall where the pipe that leads to the Coin Heaven is. You'll need Game Genie code YLLLLI (or AOSUZI) to reach the goal.

Lost Level 7

Game Genie codes:

This seems to be all of the unused rooms of an unused fortress level. The level is loaded with Tanooki suits. There's so many that every room has them. You'll want an additional Game Genie code, such as YLLLLI (walk through walls) or AOSUZI (pull blocks out of walls), to explore the level thoroughly. Ceiling pipes can't be entered, wall pipes take you back to the map screen, and ground pipes take you to blank underground areas. Because the underground areas are blank, you'll just drop into a pit. There's no boss battle, so the wall pipes and ground pipes are the only way out.

Lost Level 8

Game Genie codes:

Grass level that contains Kuribo's Shoe. One very strange thing about this level is that there's a single coin floating in the middle of nowhere.

Lost Level 9

Game Genie codes:

Another cloud level, featuring an unused enemy: green Parabeetles. The green Parabeetles move faster than the red ones, and that's about all that's different about them (aside from their color). The red Parabeetles are also in this level, so they were originally going to be in more levels.

Lost Level 10

Game Genie codes:

The shortest lost level, and the return of both Parabeetles. Considering it's extreme shortness and the fact that the Coin Heaven music plays here, I think it's much more likely that this is a bonus area similar to Coin Heaven rather than a regular level. There are no Game Genie codes right now to access it, so an IPS Patch is required.

Lost Level 11

Game Genie codes:

A very short cloud level. These cloud platforms are used only briefly in one of World 5's levels, but it seems that they were to be used throughout this level. Strangely there's a Bullet Bill cannon here, but it doesn't fire. There is no goal, no enemies, and there aren't even any pits. The only way to exit is to wait for time to run out, or of course Reset. There are no Game Genie codes yet for this level either, so you'll need an IPS Patch if you want to play it.

Lost Level 12

Game Genie codes:

A copy of #3 with the same enemies, layout, number of coins, etc. The only difference is Mario starts out high in the air.

Lost Level 13

Game Genie codes:

A sky level similar to 1-6. About halfway through the level, there's an area with coins that you need to fly up to get to.

Lost Level 14

Game Genie codes:

An auto-scrolling underwater ice level, with another unused enemy: gold Cheep-Cheeps. These ones move faster than the others, and are usually in groups.

Lost Level 15

Game Genie codes:

Another level featuring Kuribo's shoe. The top section of the level has a lone Kuribo's Shoe and coins, while the bottom section has a couple more Kuribo's Shoes and several Spineys.

Lost Level 16

Game Genie codes:

This level is a copy of one of the plant levels in World 7. The only difference is at the beginning, there's a glitched enemy and a Piranha Plant stuck in a wall.

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Footage

__________________________________________________________________________________________________________________________ Here's some footage of mine showing all 16 lost levels, in case you can't play them or want to see them first before playing: