Super Mario World/Vanilla Dome 1

There is one secret exit on this level. About half way through you will encounter two yellow pipes coming out from the ceiling and high above in the middle a yellow brick. Bumping the brick will cause a bean stalk to grow which will lead to a key and a key hole. The easiest way to reach the beanstalk is having triggered the Red Switch (This can be accomplished by using the secret exit in Vanilla Dome 2 to reach the Red Switch Palace) which will fill in the stair case and you can easily climb up. Otherwise the easiest way is to have Yoshi with you. With Yoshi you can jump extra high and reach the beanstalk that way. This secret exit leads Mario towards Vanilla Secret 1 and from there the hidden Star Road.