Shaky-Stable Stacks

Shaky-Stable Stacks is an unused (probably unfinished) level from Super Mario 64. This level is similar to Tall, Tall Mountain and Tiny-Huge Island and might be a continuation of both of those level's themes. Accessing the level on personalized copies typically requires Mario to enter the (typically inert) Tiny-Huge Island painting between the small and large THI paintings in the THI room. The painting remains unaltered.

Geography
In this level, there are two mountains that both resemble Tall Tall Mountain in appearance but are generally much smaller. There are also three ski lifts that allow access to both mountains. One mountain is considered "shaky", and the other mountain is considered "stable", which Mario spawns at the base of. There is a single tall mushroom between the mountains.

The "shaky" side of the level is a mountain smaller than the "stable" mountain. This mountain has more bridges upwards and downwards, but those bridges may start shaking and eventually break once Mario steps on them.

The "stable" side of the level is a mountain that is larger than the "shaky" mountain. This mountain is more rigid, but it has multiple unsafe precipices and columns that make it harder to go up the mountain.

Enemies reported to be in the level include Big Steelies, Moneybags, Bob-ombs, Goombas, Fwooshes, and Thwomps.

Missions

 * 1) A SHAKY CLIMB
 * 2) A STABLE CLIMB
 * 3) THE GOLDEN STEM
 * 4) VANISHING THROUGH THE GRATES
 * 5) BREAK AWAY THE UNSTABLE WALL
 * 6) 100 Coin Star (presumably)
 * 1) 100 Coin Star (presumably)

A Shaky Climb
Mario must make his way to the top of the "shaky" mountain and collect a star on top of that mountain.

A Stable Climb
Similarly to "A Shaky Climb", Mario must make his way to the top of the "stable" mountain and grab a star on top of that mountain.

The Golden Stem
There is a mushroom with this mission's star at the middle of one of the ski lift paths in the level. To get this star, Mario must ride one of the ski lifts until it is near that mushroom, and then jump to the mushroom to collect the star.

Vanishing Through The Grates!
On the back of the "stable" mountain there is a small course with metal grates. Mario must collect a Vanish Cap and jump through the course quickly to grab a star.

Break Away The Unstable Wall
Unknown. It likely requires the player to punch a wall somewhere on the shaky mountain to access this star, but the location of the wall and by extension the star has not been found yet, if there even is one. To confuse things even further, Koopa The Quick's flag is present near Mario's spawn location in the level, even though Koopa The Quick cannot be found in this mission.

???
There is a red coin star in the level as there are red coins located throughout the level, but upon collecting all red coins the Power Star reportedly spawns out of bounds inside the stable mountain at the bottom of the level, so it has never been collected. Due to this, and because of Break The Unstable Wall's unknown power star location, the mission title is not known yet.

Theories

 * This level is likely to be a reference (if not a homage) to Meoto Iwa, two rock stacks off the coast of Futami, Mie, Japan. The ski lifts between the two mountains is similar to the shimenawa between the two rocks, and the Moneybags (which resemble and jump like frogs) reported to be in the level are likely references to the frog statues at Okitama Shrine, which is close to Meoto Iwa's location.