Tall, Tall Mountain is the twelfth world in Super Mario 64 and Super Mario 64 DS that comprises almost entirely of an enormous mountain, complete with obstacles and enemies. It's dangerous, because a vast majority of the mountain is extremely thin and is on a cliff face. At the top of the mountain, there is a flat surface and railing, complete with a waterfall that will transport you to the bottom of the level.
Just as the painting depicts, Tall, Tall Mountain is surrounded by giant Mushrooms. One of these giant Mushrooms will be of some use, since it will contain a Star, and a Star Point where a Star appears after collecting 8 Red Coins.
Some of the main enemies in the course are Ukiki (expect the one who gives a Star), who will steal Mario's hat, and Fwoosh, who'll attempt to blow it off the mountain. Without his hat, Mario becomes weaker and takes more damage per hit.
Star 1: Scale the Mountain
This star is relatively easy to get. As its name suggests, Mario is tasked to go to the top of the mountain. It seems simple enough, but the coarse is riddled with pits, enemies, and several dangerous obstacles. Atop the mountain is the star. This can be done with the owl.
Star 2: Mystery of the Monkey Cage
This is also another easy star to get. Mario must head to the very top of the mountain where he must catch an Ukiki. After Mario grabs the, the Ukiki will take Mario to the Star that is being held in the cage. Mario must follow the monkey a little ways back down the mountain to earn this Star. In the DS version it is easier to do with Yoshi, as he has the move 'Eat' which he can use to catch Ukiki. Instead of climbing the mountain, the heroes can fly with the owl, and do the ground pound while falling.
Star 3: Scary 'Shrooms, Red Coins
Another Red Coin hunting mission. Mario must hop around the mushroom orchard and grab the red coins that are laying about. Some of them are on nearly out-of-reach mushroom where he should be careful not to fall off. The Star would appear on one of these mushrooms which Mario must safely get. In the DS version, it is safe to do this mission with Yoshi, as he can do the Flutter Jump.
Star 4: Mysterious Mountainside
Make your way over to where the Fwoosh is, but go to where the line of coins are, and find the secret entrance to the slide. On your way down, make sure you take the path to your left, or you'll hit a dead end. After sliding down, you'll find a hole that will drop you into a cage, and the star is being there. The owl can be used to go higher and do a shortcut. Luigi can use a power flower to turn invisible and somersault to the cage in the DS version.
Star 5: Breathtaking View from Bridge (N64)/ Breathtaking View from the Bridge (DS)
Mario must head back to the very top of the mountain like he did in the second mission. However, he must go the right way until he sees a waterfall with a little ledge near it. He must Wall Kick safely down to get to the Star. This is easier to do with the owl.
Star 6: Blast to the Lonely Mushroom
This star can be a little tricky to get. First, Mario must talk to the pink Bob-omb in order to activate the cannon. Next, he must then jump back to the mushroom where get got the star from in the third mission. Mario then must take a secret path that leads to the cannon and launch himself at the star, or the easier way is the owl. In the DS version, Luigi can somersault to the mushroom star.
Star 7: 5 Secrets of the Mountainside (DS)
Once more, make your way up to the top of the mountain, except now, there should be a red ? Block. Smashing that as Mario will give you a wing cap, allowing you to fly around the mountain. There should a be five rings of coins, with a single coin in the middle of each one. Collect the five middle coins in order to gain this star. The star should spawn near the ? Box you got the Power Flower from. This can be done with the owl too.