Multifamily residential (also known as multidwelling unit or MDU) is a classification of housing where multiple separate housing units for residential inhabitants are contained within one building or several buildings within one complex. Units can be next to each other (side-by-side units), or stacked on top of each other (top and bottom units). A common form is an apartment building. Many intentional communities incorporate multifamily residences, such as in cohousing projects. Sometimes units in a multifamily residential building are condominiums, where typically the units are owned individually rather than leased from a single apartment building owner. History Before the Industrial Revolution, such examples were rare, existing only in historical urban centers. In Ancient Rome, these are called insulae, skyscrapers in Shibam, malice houses in Madrid, and casbah in the Casbah of Algiers. Examples Apartment building or block of flats - a building with multiple apartments. There can be multiple apartments on each floor and there are often multiple floors. Apartment buildings can range in many sizes, some with only a few apartments, other with hundreds of apartments on many floors, or any size in between. There are often inside hallways and inside entrances to each apartment, but outside entrances to each apartment are also possible. An apartment building can be owned by one party and each of the apartments rented to tenants or each of the apartments can be owned as a condominium by separate parties. Mixed use building - a building with space for both commercial, business, or office use, and space for residential use. Possible arrangements include the commercial/business use on the first or first couple floors and one or more apartments or residential spaces on the upper floors. Another possibility is to have the commercial/business area up front and the residential area in the back. Some or maybe all of the space may be used by the owner or some or all the business and residential units may be leased by the owner. Condominium ownership is also possible. Apartment community - a collection of apartment buildings on adjoining pieces of land, generally owned by one entity. The buildings often share common grounds and amenities, such as pools, parking areas, and a community clubhouse, used as leasing offices for the community. Brownstone: a New York City term for a rowhouse: see rowhouse. Bedsit: a British expression (short for bed-sitting room) for a single-roomed dwelling in a sub-divided larger