The game’s second warp cannon entrance is unlocked within world 2-6.

The pipe leads to a hidden flag pole exit, and jumping on the flag will open up the path to the warp cannon on the world map. Immediately past that you should enter a hidden warp pipe. Walk along the top of the ledge until you pass a small dip where you become visible. Alternatively, you can simply jump once then shake your controller to hop off Yoshi’s back and get a little extra height. Jump, then press jump again to have Yoshi boost you up the extra few inches you’ll need to reach it. The real secret path is just off the top of the screen above the ledge. If you continue into the floating mass from the ledge, you’ll discover a hidden passage, ignore it. There are three smaller plateaus below it that you can use to reach the ledge.

Shortly after the mid-level save point, you’ll come across a large floating mass in the sky with a tiny ledge just visible at the top of the screen. Make sure you don’t lose him during the level, as you’ll need his help to gain entry to the warp cannon. You’ll make your way through the level and eventually find a ? box containing your old pal Yoshi. The game’s first warp cannon entrance is located in World 1-3. New Super Mario Bros Wii is no slouch in this department, as there are several secrets for careful explorers to unlock. No Mario game would be complete without a multitude of unlockable warp cannons.

New super mario bros ds world 1 cannon