New Super Mario Bros./World 7

World 7 is one of two optional worlds in the game, in that it can be skipped entirely when beating the game. This secret world is unlocked by defeating Petey Piranha as Mini Mario or Luigi, back in World 5. World 7 has a sky theme, so many of the courses are high in the sky and have a heavy focus on accurate platforming. It has several Toad Houses, with green ones being the most numerous. It also has a fair amount of secret exits, and at least one must be found to reach the castle.

World 7-Ghost
After hitting the P-Switch, try running to the left instead. As you pass by some brick blocks overhead, look for one block that has a glimmering effect. This signifies that the brick block is actually a disguised question mark block, and hitting it causes a vine to grow. Get on to the block before the other brick blocks revert to coins, then climb up the vine to reach an alcove with a door. The door leads to the secret exit of the ghost house, where the red flagpole can be found.

This secret exit creates a shortcut to the World 7-Tower, skipping two levels while opening a green Toad House for you to use.

World 7-4
You'll need to be in your Mini form for this secret exit. Once you've bounced from the tallest pink mushroom, look for a flying block near a wall to your left and land on it. Jump to the narrow alcove, then make a jump to loop around the wall above the alcove and drop into the small valley with the mini warp pipe. Take the warp pipe to get to the red flagpole.

This secret exit skips straight to the World 7-Castle, letting you skip the confusing network of levels that comprise the second half of World 7 and opening a green Toad House as well.

World 7-5
Right before the Banzai Bill Blaster, there is a small hill of brown blocks covering the entrance of a warp pipe in the ground. The lone Bob-omb can't destroy enough blocks to let you access the warp pipe, so you have to get the Bob-omb before it to the right of the rotating Bill Blasters, and use both Bob-ombs to make a large enough hole to reach the pipe. If positioning Bob-ombs while being fired on from all sides is two difficult for you, you can simply use a Mega Mushroom to tear through the blocks. Once the warp pipe entrance is available, go into it to enter a cave. Go right and up the right warp pipe to be taken to the red flagpole.

This secret exit creates a path to World 7-A, just one of several paths to the castle in the convoluted second half of World 7.

World 7-6
After the checkpoint, there are two brick block platforms arranged parallel to each other, with Paratroopas hopping underneath. First, you must destroy the middle brick block of the top platform. Then, hit the middle block of the bottom platform from below to make a vine grow into the sky. Climb up it to reach a bonus area. Get on the mushroom to make it move. Stay on the mushroom as it goes toward the right. You can make small jumps to get coins, including the first Star Coin of the stage. Eventually, you will reach a thin platform with a pipe above it. Go into the warp pipe to arrive at the red flagpole.

This secret exit creates a path to World 7-7, one of three paths that allow you to continue onward to the castle.