Magic Mushroom Cave

Magic Mushroom Cave - is an area in B3313.

Description
After exploring the mountain, Mario/Luigi fall into a cave, or rather an abyss, filled with magical colorful mushrooms. The abyss washed by the waterfalls also contains traces of some kind of construction, as evidenced by bridges and a hut leading back outside.

But what catches eye is the giant rainbow mushroom in the center with protrusions and a star on top. Below it are also the aforementioned mushrooms, but during platforming on them, Mario/Luigi will be disturbed by the fly guys.

Origins
This appears to be an original creation.

The BoB theme from the vanilla game OST plays here.

Talking with Ukiki on a green mushroom:
IF YOU NEED TO STAY HIGH,

GRAB, HOLD AND HANG ON

Stars

 * Jump onto the ledges and grab the star on top of the rainbow mushroom.
 * Follow the lower mushrooms and, dodging the fly guys, reach the yellow mushroom with a star.

Leading here

 * Tall, Tall Mountain (beta): Jump into the hole at the top of the mountain.

Two-way

 * Tall, Tall Mountain (beta): Enter the hut.