Super Mario World/Donut Plains/Donut Secret 2
Donut Secret 2 can be accessed using the secret exit in Donut Secret House. It's an underground level, made mostly out of ice. Lots of Spike Tops and Koopas. After clearing two Jumpin' Pirahna Plants a green pipe will lead to an above ground bonus level. YOu can pass that level with or without the P-Ballon that's inside the ? block. With the ballon you will be able to get more coins.