Dilapidated spiral staircase in an equally dilapidated residential building in Habana Vieja.
Note the wires from the flats to the individual electricity meters.
I learned that overpopulation of flats is endemic in Havana as people from the country move to the city, rent a small place, and later bring their families, staying in the same small place. To optimise on the height of the old colonial buildings, many improvise mezzanine floors without there necessarily being load bearing walls to support this. I heard that this often leads to the floors caving in, leaving empty shells of buildings which are then quite often used as city carparks