apartment buildings are multi-story buildings where three or more residences are contained within one structure. such a building may be called an "apartment building", "apartment complex", "flat complex", "block of flats", "tower block", "high-rise" or, occasionally, "mansion block" (in british english), especially if it consists of many apartments for rent. a high-rise apartment building is commonly referred to as a "residential tower", "apartment tower", or "block of flats" in australia.