Havana and Cuba in general is a paradise for architectural photographers. With building that range from falling / fallen down to pristine renovations there's something for everyone. Whether you're inclined to wide, full building views or close ups of the varied and interesting details there's something for everyone.
Every street is unique and I personally really enjoy walking through all of the streets and alleys in search of both great architecture as well as interacting with the locals who are often outside throughout the day and nights.
Shot with a Sony RX1 utilizing a fixed, Zeiss 35mm lens set to F4 at 1/250 sec.