Where is the impossible space?

I found a post on the steam forum about this

People are discussing the different things they have found in a thread. From the first post

"I've been noclipping around looking for it, and think I might have found it.

When GLaDOS drops you into the incinerator vent after her awakening, the vent hole is a two-way portal to a long shaft down. This is because the shaft's "official" location actually contradicts part of the level we're shown off in the distance while mucking about underneath her. Without the portal approach, those map elements would collide."

The impossible space is a space that the player can reach where it should not fit. (ex. Walking into a small house and ending up in a large warehouse) During the part that was mentioned in the last post the player's body is removed from the player's camera and is not present throughout that scene, so that cannot be the impossible space because the player is not physically there, although it does fit the requirements in some ways. Personally I think it is the Borealis AKA. the missing experiment achievement, it just doesn't seem to fit right to me. I'm probably wrong but that's my thoughts on it, I haven't done any noclipping yet so I don't know if it fits or not.

The impossible space(s) from what I have found are the testing spheres in old Aperture. When going down the shaft and first walking into the salt mine where the testing spheres are you get a sense for their size compared to the elevator going into the bottom of them. When finally getting into the testing sphere, you notice that it is much much larger than what it appeared from the outside.

its obvious,
SPOILER
when u complete the game and glados kicks you out you will see a little shed where you just got kicked out, its probably just a joke lol

@moneyman112
You go up an elevator, surely the top of the shaft could fit in the shed.

I beat the game twice. And i agree, it's the incinerator shaft.

It also can't be the testing spheres, since there's a loading screen when you get into the elevator.