Princess Peach's Castle/Second Floor

The second floor of Princess Peach's Castle is an area accessed in the latter half of Super Mario 64. After collecting 31 stars and defeating Bowser in Bowser in the Fire Sea, Mario can use the key to access the second floor of the castle.

Geography
The second floor can be found past the double door located up the stairs in the main foyer. These doors lead to a spiral staircase that leads up to the second floor itself.

The second floor is a donut-shaped room with blue sky-like walls. It has many paintings which cannot be entered, except for a few: a painting of a Skeeter leading to Wet-Dry World, and a painting of Tall, Tall Mountain. There's a staircase on this floor that leads up to the third floor of the castle.

There is a door that leads to a triplet of identical paintings, all with different sizes. An example of perspective trickery has the room get progressively smaller or progressively larger, approaching the smaller and larger paintings. This leads to Tiny-Huge Island.

Mirror Room
There is another door, surrounded with brown bricks, which leads into the infamous mirror room. This room is characterized by its large mirror, which mirrors Mario and the Lakitu filming him. There are a series of paintings in the room, although there is a bland wall that appears as a snowman painting on the other side of the mirror. This empty wall leads to Snowman's Land.

Broken Paintings
Found in the main room, in addition to the ones for Wet-Dry World and Tall, Tall Mountain are several paintings that normally cannot be entered. Most of these are duplicates of first-floor paintings, with the exception of two paintings of the sun around Wet-Dry World's and the one on the central staircase, which depicts clouds and a starry sky.

Some copies however allow certain of these to be accessed under certain circumstances. While a sun painting may be accessible from the start, the others usually need to be unlocked somehow. The means of doing so vary by individual painting, and many in most cases still remain inaccessible and cannot be unlocked.

Please walk quietly in the hallway
Although isn't an actual phenomenon, the textbox's real meaning is a mystery, because the place it is seen in is not a hallway, instead a corridor and walking quietly will have no effect, and neither does running or making noise.

In the first video of Greenio's odd findings, it is theorized that the textbox would have been used in the basement, specifically, to not wake up Wario.

Mirror Room Negative Emotional Aura
Although by far not as common as the "negative emotional aura" of Wet-Dry World, occasional players have reported experiences of strong dread and loneliness associated with the Mirror Room. This negative emotional aura is reportedly even worse than that of said level, and has resulted in players quitting to the main menu or even turning off the console after visiting the room.

Player reports
Ghoulstoat94: For some reason, I began to feel alone while adding the section of this page above. It made me forget that I have several pets at home. Then I began to feel a sense of dread, which caused me to get up and turn on my lamp. The light from my lamp only temporarily alleviated the feeling. I tried to ignore the feeling, but eventually I couldn't stand it any longer. So I stood up and went to the kitchen to pet the dog and get a bottle of water. The feeling has passed, but I'm not going to stay on this page any longer in case it returns.