It’s been 28 years since Super Mario 64 was released on Nintendo 64, but players have finally been able to solve one of its last remaining mysteries. A lone cabin door at the bottom of the game’s fourth course, Cool, Cool Mountain (aka. Snow World) was previously thought to be unopenable from the outside, setting it apart from the majority that players come across in the game which open both ways. The door is clearly fully functional, as Mario has always been able to use it from the inside after diving into a chimney at the top of the mountain and going down a slide, but hitboxes prevent players from making their way back through it after leaving the cabin.

https://screenrant.com/super-mario-64-mystery-door-cool-mountain-opened/