Nearly 28 years after Super Mario 64 first launched in Japan in June 1996, one of the game’s oldest mysteries has finally been solved — and no cheat codes were used. A locked door in the Cool, Cool Mountain level, long thought to be just decorative, was recently opened in a fully legitimate way. It is an incredible discovery of a game that is almost 30 years old, which was thought to have been 100% unraveled. Find out what was behind the door.
The mysterious door in Cool, Cool Mountain
When Super Mario 64 launched in 1996, it changed everything about platformer games. Among its many memorable levels, Cool, Cool Mountain stood out for its snow-covered slopes and icy slides. But one detail always puzzled players: a door that can be opened from the inside, but once you cross it, you cannot go back. On the outside, it is presented with no handle, no key, and so, no clear purpose.
Over the years, many fans have tried unsuccessfully to pass through this door, which was left without a lock by the developers to indicate the inability to open it. Some thought it may have led back to a secret room, others believed it was unfinished content left in by the developers, or simply just accepted the fact that it just could not be opened.
The purpose of this door was not clear, but it was finally discovered that it was just taking it to the inside of the cabin. But what exactly were the steps to be able to open this door, which, at first, was designed to remain closed?
A hidden passage unlocked — without hacks
Last year, in 2024, Super Mario 64 speedrunner “Alexpalix” finally got in — using only the original game engine, without hacking or modifying the code based on a video from the acclaimed Super Mario 64 expert, pannenkoek2012, about the logic behind invisible walls in the game.
The key to unlocking the door was using a complex method that relies on exploiting how the game engine renders Mario’s position in 3D space. Alexpalix followed a specific series of steps and managed to guide Mario through the door, which had working collision physics. It wasn’t just a visual detail; the game actually recognized it as passable space.
In summary, the way of interaction between the game’s objects, called collision, which is basically the reason why the player cannot open the door, was also the secret to uncovering its opening. The strategy was to make the mother penguin, present in the external part of the game for this phase, get close enough to make the collision glitches even bigger, allowing the door to be opened through a skilled maneuver.
Why this discovery matters
This find is not just a curiosity. It shows that even after nearly three decades, classic games can still surprise us. It also highlights the dedication of fans who go deep into a game’s code and geometry, not necessarily to break it, but to understand its mechanics. At this point, many believed Super Mario 64 had no more secrets. Speedrunners, modders, and data miners had seemingly explored it all. Yet, this unassuming door sat there, untouched, waiting for someone with the right tools and mindset to uncover its purpose.
The opening of this door is just one example of how we can still be surprised to this day with new discoveries in the classic and acclaimed world of Super Mario 64. As technology improves and our understanding of game engines deepens, it’s entirely possible we’ll see more hidden areas or other tricks come to light.
