Inarchitecture, anatrium (pl.: atria or atriums)[1] is a large open-air orskylight-covered space surrounded by abuilding.^[2]Atria were a common feature inAncient Roman dwellings, providinglight andventilation to theinterior. Modern atria, as developed in the late 19th and 20th centuries, are often several stories high, with aglazed roof or largewindows, and often located immediately beyond a building's main entrance doors (in thelobby).

Atria are a popular design feature because they give their buildings a "feeling of space and light."^[3] The atrium has become a key feature of many buildings in recent years.^[4] Atria are popular with building users, building designers and building developers. Users like atria because they create a dynamic and stimulating interior that provides shelter from the external environment while maintaining a visual link with that environment. Designers enjoy the opportunity to create new types of spaces in buildings, and developers see atria as prestigious amenities that can increase commercial value and appeal.^[5]

In adomus, a large house inancient Roman architecture, the atrium was the open centralcourt with enclosed rooms on all sides. In the middle of the atrium was theimpluvium, a shallow pool sunken into the floor to catchrainwater from the roof. Some surviving examples are beautifully decorated. The opening in the ceiling above the pool (compluvium) called for some means of support for the roof, and it is here where one differentiates betweenfive different styles of atrium. As the centrepiece of the house, the atrium was the most lavishly furnished room. Wealthier houses often included a marblecartibulum, an oblong marble table supported bytrapezophoros pedestals depicting mythological creatures like winged griffins.^[6] Also, it contained the little chapel to theancestral spirits (lararium), the householdsafe (arca) and sometimes a bust of the master of the house. The cylindricalputeal (a wellhead) gave access to the water cistern fed by water seeping through the porous bottom of the overlying impluvium. The atrium contributed to thepassive cooling of the house.

The term was also used for a variety of spaces in public and religious buildings, mostly forms ofarcaded courtyards, larger versions of the domestic spaces.Byzantine churches were often entered through such a space (as are manymosques, though the term atrium is not usually used to describeIslamic architecture).

The 19th century brought the industrial revolution with great advances in iron and glass manufacturing techniques. Courtyards could then have horizontal glazing overhead, eliminating some of the weather elements from the space and giving birth to the modern atrium.

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  Victoria Hall inHalifax Town Hall, 1863
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  Atrium at the center of theBradbury Building in Los Angeles

Fire control is an important aspect of contemporary atrium design due to criticism that poorly designed atria could allow fire to spread to a building's upper stories more quickly. Another downside to incorporating an atrium is that it typically creates unused vertical space which could otherwise be occupied by additional floors.

One of the mainpublic spaces atFederation Square, inMelbourne, Australia, is calledThe Atrium and is a street-like space, five stories high with glazed walls and roof. The structure and glazing pattern follow the system offractals used to arrange the panels on the rest of the facades at Federation Square.

InNashville, Tennessee, U.S., theOpryland Hotel hosts 4 different large atria, spanning 9 acres (36,000 m²) of glass ceiling in total, in the hotel above thegardens of: Delta, Cascades, Garden-Conservatories, and Magnolia.

When it opened in 2019, theLeeza SOHO inBeijing, had the world's tallest atrium at 194 metres (636 ft), replacing the previous record-holder, theBurj Al Arab inDubai.^[7] TheLuxor Hotel, inLas Vegas,Nevada, has the largest atrium in the world (by volume) at 29 million cubic feet (820,000 m³).

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  The atrium of1 Bligh Street, aSydney office tower, looking upwards
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  Looking up inside the 32-story atrium of the Shanghai Grand Hyatt, part of theJin Mao Building
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  Atrium of theNew York State Theater atLincoln Center
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  The Grand Piazza atrium inside theSuperStar Virgo
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  Four floor atrium of Gould Hall,College of Built Environments, at theUniversity of Washington
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  TheGrand Doubletree hotel/condo inDowntown Miami 42 story atrium
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  Atrium ofComplexe Desjardins,Montreal
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  Atrium of Kurayoshi Park Square inKurayoshi,Japan
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  Multi-flooratrium with three see-throughoctagonalelevator shafts inWater Tower Place inChicago
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  Interior of Wilson Hall atFermi Lab inIllinois
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  Main atrium ofPiarco International Airport
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  Atrium of aMyer store inMelbourne, looking from the top floor to the ground floor
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  An atrium exterior of the200 Public Square building inDowntown Cleveland,Ohio.
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  Atrium (architecture)Salem, Massachusetts PEM *Peabody Essex Museum
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  Anadumuttam, or the central atrium of aKeralaNālukettu.

• Cavaedium
• Courtyard
• Panopticon
• Quadrangle

• "Atrium" .Encyclopædia Britannica. Vol. III (9th ed.). 1878. p. 50.
• Roth, Leland M. (1993).Understanding Architecture: Its Elements History and Meaning. Oxford, UK: Westview Press. p. 520.ISBN 0-06-430158-3.