This food bar in the access lane between 2 buildings with its crappy hand written oil-stained cardboard signage and the home made DIY shelves has been there for well over 10 years.
In the early 90s, the Taipei government legalized all illegal structures built before 1989 as it proved impossible to dismantle 1/3 of the city- obviously. My guess is, this closet of a shop must’ve been left from that time. There is quite a steady stream of customers within this 1.5m wide shop throughout the day. Perhaps the food tastes extra good without any refrigeration. As to accessing the backs of the 2 buildings from the street, the tenants must have found other alternative ways.
