The zone of the boundary between the interior and the exterior space could possibly be outlined as a wider set of things, with the window port as the sole point of intersection. This zone is a point of interaction of different spatial conditions, functions and uses, in which they coexist and evolve parallelly, although they differ conceptually and topographically. The exterior forms the divided form of the interior as an extension. The threshold in this case is represented by the transparency. Transparency due to its particular material properties operates either as an optically translucent surface or as a mirror. It depends on the position of the observer. But who is the observer and who is being observed? It might be argued that the observer status is attributed to the person standing in the interior. But what exactly is interior? The position is relative. You are standing inside your home, so the exterior includes everything but that. Although, when you are standing in your balcony you are basically located outside your home. Until you pass by the doorstep, the balcony is being considered as exterior. Then, the exterior consists of everything except your balcony. Transparency is derisive. It reverses the characterisations that we hurriedly assigned. The same applies to the balcony. Transparency is a boundary between the safe and the unexpected space. The balcony on the other hand is the boundary between the ultimate point of property and the rest of the world that unfolds around it. In the context of this research, we analyse theories related to the concept of boundary, we exhibit data related to the "transparent" architecture and we analyse the typology of the Greek “apartment building of the consideration”. Finally, as a point of reference all the above, we define this specific area, at the student’s appartments, in the city of Volos, as the main subject of the research.