> Inside, wide corridors ("streets in the sky") run along the central long axis of every third floor of the building. Each apartment lies on two levels, such that the room on one side of a corridor belongs to the apartment that is mostly below the corridor floor, while that on the opposite side belongs to the apartment above. On those floors without corridors, the apartments stretch from one side of the building to the other, and each has a balcony on the western side.

If you search for floorplans of it, it looks like there are also interior corridors but I think every apartment has access to one of those wide corridors. I'm not sure what the point of having both interior and exterior corridors is, I would think it would be better to get rid of the interior corridor and give the extra space to the exterior one.

https://en.wikipedia.org/wiki/Unit%C3%A9_d%27habitation#La_C...

Edit: Well this is disappointing. After further research, it looks like that corridor is just the main one and the rest of the floor have dark, internal corridors and then enclosed balconies. What a missed opportunity, imagine a whole building full of corridors like the ones in the image, if you're going to build two story apartments then why not do it that way?

Can't say for sure but here's a 15min video with a tour of it https://www.youtube.com/watch?v=J-ISAAZsq4Y