SAH Archipedia uses terms from the Getty Art and Architecture Thesaurus (AAT) to categorize and classify metadata for the entries in the database. For more information on the Getty AAT, click here.

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obelisks (monumental pillars)
Tall, slender, four-sided, usually monolithic stone shafts which taper upward and end in a pyramidal tip.

observation decks
Spaces designed for viewing a landscape, or observing wildlife. These may be open spaces at the tops of tall buildings or constructed in natural environments.

Buildings or parts of buildings set apart for, and equipped with instruments for making, observations of natural phenomena, typically astronomical, meteorological, or geophysical phenomena.

octagonal plan
Plan of a building or city that is arranged within an octagon (eight sides of equal length), usually a centralized plan.

office buildings
Buildings constructed or used primarily for offices, which are spaces where business, administrative, or professional activities are conducted.

office complexes
Building complexes that house offices and facilities for the support of the offices.

office parks
Areas of land or property where many office buildings may be grouped together and developed specifically to attract corporate offices.

office towers
Skyscrapers or other tall buildings primarily containing offices, which are spaces where business, administrative, or professional activities are conducted.

officers' clubs
Spaces set aside for military officers to engage in social interaction and consuming refreshments.

offices (administrative entities)
Departments or administrative entities, often governmental, responsible for particular activities or duties, having a head and senior officials.

offices (work spaces)
Rooms where business, administrative, or professional activities are conducted.

official residences
Residences of heads of state or other public officials.

oil fields
Areas of land or seabed under which are found oil-bearing strata, particularly when the oil is found in pools and in amounts large enough to support commercial exploitation.

oil mills
Factories equipped with machines for extracting vegetable oils.

oil storage tanks
Tanks used to store oil, but not used to supply the oil to the equipment for which it is intended.

oil wells
Wells driven into rock from which petroleum is obtained.

old towns
Older, often historic, sections of cities or towns, generally distinguished from newer parts by clear boundaries and distinctive architecture.

one-room schools
Small educational buildings, generally consisting of one major teaching space, and often built to resemble meeting houses, churches, or dwellings. Use when emphasizing the size or form of such buildings; when emphasizing the function or location of some early examples, prefer "rural schools."

open plan
Plan of a building or city that is arranged to most conveniently accommodate the flow of traffic, activities, or work that goes on inside it, instead of along an axis or radiating from a central point.

open spaces
Spaces in urban environments designed as passages for pedestrians, and as social spaces, not as clearly delimited as parks, but sharing some of the same characteristics. Often these function as utilitarian connecting spaces between buildings, or simply as an open area designated by a municipal authority, but without the amenities or formality of a park.

open-air museums
Carefully selected and situated collections of original buildings designed to illustrate not only the architecture and building forms of a given geographical area and period, but also to recreate the atmosphere and lifestyle.

open-air theaters
Theaters designed with facilities for outdoor performing arts productions.

open-air zoos
Zoos in which many or all of the animals have access to open-air enclosures that resemble the animals' natural habitats, in contrast to early zoos where most animals were confined to relatively small cages. Zoos in which many or all of the animals have access to open-air enclosures that resemble the animals' natural habitats, in contrast to early zoos where most animals were confined to relatively small cages.

opera houses
Concert halls designed specifically to accommodate the production needs of opera performances.

operating rooms
Specially equipped rooms, usually in hospitals, where surgical procedures are performed.

Greenhouses designed to shelter through the winter tropical, and often ornamental, trees such as orange trees, and usually with southern exposure and heating systems.

Farms devoted to the cultivation of fruit or nut trees.

orchestra pits
Sunken spaces in front of the forestage from which an orchestra plays.

orchestras (audience spaces)
In modern theaters, the entire main-floor space for spectators.

organ lofts
Galleries or lofts in which an organ is located, often in a church and intended mainly for use by the organist and choir. It is often connected to the organ, with which it may form a single architectural-decorative structure. In some regions, the organ loft is very large, often consisting of several superimposed levels, and is reserved for men attending Mass. It is usually made of wood or stone, supported by ledges with a parapet and sometimes grilles that conceal the members of the choir. It is usually located in the western portion of the nave, above the main entrance to the church, sometimes supported by the inner door. It may also be located in other parts of the nave, in the arms of the transept, or along the walls of the choir.

oriel windows
Bay windows projecting from an upper floor and not extending to the ground; usually supported by brackets or corbels.

orphanages (buildings)
Buildings that house facilities for the housing and care of orphans, who are children whose parents are either dead or otherwise unable to care for their child.

Detached buildings separate from a main building. Detached buildings separate from a main building.

outdoor cafés
Restaurants designed or utilized for dining outdoors at tables surrounding the building, often with tables placed in a patio or on a sidewalk in an urban area, sometimes with a protective roof or umbrellas sheltering the tables. Outdoor seating may be offered only seasonally as weather permits, with additional seating available indoors.

outdoor sculpture
Sculpture designed to be placed outdoors. For contemporary outdoor works that especially exploit or incorporate aspects of their sites, use "environmental art."

Detached structures in domestic contexts containing one or more seats and a pit serving as toilets; distinguished from "latrines" which are similar structures in public contexts. For rooms that are within buildings and have such simple facilities, use "privies."

outlet stores
Retail stores where manufacturers sell their stock directly to the public through their own branded stores, typically at prices lower than in other stores.

outpatient clinics
Facilities that provide medical treatments outside a hospital on an outpatient basis, that is, without accomodating overnight admissions.

outsider art
Refers to art created or collected according to a philosophy of avoidance of the conventional fine art tradition. The concept generally refers to art that fits the ideal described by Jean Dubuffet, who posited that art should be inventive, non-conformist, unprocessed, spontaneous, insulated from all social and cultural influences, "brut," created without thought of financial gain or public recognition, and based upon autonomous inspiration, in direct contrast to the stereotypes of the traditional or official artistic culture. Dubuffet sought such art in the work of psychiatric patients and other insulated individuals. It is generally distinct from "naive art," which is created by those without formal training, but not necessarily in accordance with the principles described above. It is also typically distinct from "folk art," which is made according to the rules and traditions of a particular culture.

Projections of roofs or upper stories beyond a story immediately below.

Open spaces, such as a cliff, that affords a scenic view or vista.

overmantels (interior wall components)
Panels or ornamental structures situated above mantels.

Highway or railway bridge crossings over some barrier, as another highway or railroad tracks.

Cleared but unpaved areas at the end of runways offering extra landing roll to an airplane in an emergency.

owner-built houses
Houses that have been constructed by the owners rather than by a professional building company or architect, whether or not the plan was designed by a professional architect.

oxbow lakes
Crescent-shaped lakes left in the sites of former river meanders.

oxbows (meanders)
River meanders with extreme curvature such that only a neck of land is left between two parts of the stream.