my building (one of 6 identical hi rise apartment buildings) has cat walks.

Every apartment in the building has a terrace (a covered out door "room"--(terrace is NYC term, balcony is perhaps more common)

the elevator comes up to a small hall (about 8 by 20)
it holds the elevators, an entry to stailwell, the 'garbage shut room) 2 apartment doors, and 2 exits.

the exits open to (covered but open) cat walks.
from these catwalks there are entries to smaller 'halls" --my apartment has a hall about 4 by 6 (feet) (1.3 by 1.9meters)
there is an entry door, and 3 apartment doors.

Out door 'halls'(cat walks) like this are pretty common at motels, (and they are not uncommon in NYC in middle class housing from late 1950 to early 1970's.. (they were popular for a time.. its passed)

my other obsession