Instructions
Enter Level 2 in World 8. The secret level in World 8 can only be accessed by finding a secret exit in this level.
Play through the level normally until you reach a yellow pipe on top of a red pipe, both of which will be producing goombas. Jump over these pipes and walk down to the area with two small red bridges, one slightly higher than the other.
Jump on the moving stone wheels to the right of these bridges, but don't continue moving to the right of the screen. Instead, walk through the rock to the left of the very first stone wheel. Follow this path and exit through the hidden pipe.
Follow this new path until you reach the end-of-level flagpole. Finishing the level in this manner will open the path to the hidden level.