Side of the wall from neighbour side, which is one of the four walls of the airshaft/light shaft of the building and that indicates the light shaft is located at the end of the building, adjacent to the neighbor's building.

The air shaft is a vertical shaft that is carefully implemented in buildings as a design solution to provide daylight and natural ventilation for interior spaces [19].
https://www.researchgate.net/figure/Air-behaviour-of-the-con...

In architecture, a lightwell,[NB 1] sky-well,[NB 2] or air shaft is an unroofed or roofed external space provided within the volume of a large building to allow light and air to reach what would otherwise be a dark or unventilated area. Lightwells may be lined with glazed bricks to increase the reflection of sunlight within the space. Lightwells may have sunlight reflecting mirrors on the top of light well.[1]
https://en.wikipedia.org/wiki/Lightwell

In subterranean civil engineering, ventilation shafts, also known as airshafts or vent shafts, are vertical passages used in mines and tunnels to move fresh air underground, and to remove stale air.[1]
https://en.wikipedia.org/wiki/Ventilation_shaft