Kill the Koopa Troopa, then stand on the white block and duck down for five seconds, you will then fall behind the scenery. In Level 1-3, progress through the level until you come across a white block (there's a red Koopa Troopa walking on it). If you wish, you can complete the game very quickly by collecting both whistles from World 1, using one, then using the other while in the warp zone, which allows you to instantly go to World 8. Two can be found in World 1, another can be found in World 2. There are only three warp whistles in the game.

Warping from worlds 7, 8 or the warp zone itself takes you to the bottom path.From here, you can warp to worlds 5, 6, and 7. Warping from worlds 2, 3, 4, 5, or 6 takes you to the middle path.From here, you can warp to worlds 2, 3, and 4. Warping from world 1 takes you to the top path.

There are three paths, and which one you land on depends on which world you use the warp whistle in: These items, when used, take you to a special warp zone map, which allows you to warp to another world (pictured on the right). 3 equivalent to the Warp Zones from the original Super Mario Bros.

The warp whistles are the Super Mario Bros.

Super mario bros 3 world 8 fortress 2