I was thinking about how to enter the design. My idea at this point is to have the building on the side of the building, similar to 'rucksack house'.
To enter this then becomes a problem. However, the answers to the problem were with Michael. In prison break, the characters have to escape a situation using a wire connecting one of the buildings to the exterior wall. The use it to climb across.
Therefore, I began thinking if this could be the solution to the problem of accessing the space.