In every decade since its founding, Washington has been the recipient of buildings containing spacious and magnificent rooms. In fact, rooms inside buildings are sometimes more awe-inspiring and memorable than the buildings themselves.

Hotels, with their ornate lobbies and grand ballrooms, as well as luxurious mansions, embassies and theaters have added just such spaces to the city's growing collection of monumental spaces and buildings, most of which were built by government agencies.

But until the 1950s, both in Washington and other American cities, very few buildings of any type followed the example of the Old Pension Building, constructed in the 1880s and organized around an immense, roofed central void whose visual, functional and symbolic mission was paramount to the building as a whole.

The notion of incorporating a covered atrium in privately financed, profit-motivated commercial buildings must have seemed economically unfeasible and architecturally inappropriate to American entrepreneurs and designers during the 19th century and the first half of this century. Perhaps they were persuaded by the continuing appearance of courtyards of one sort or another only in buildings sponsored by institutions or governments and devoted to national, public purpose.

Notable examples of such buildings in the heart of the nation's capital include:

*The Library of Congress, designed by Smithmeyer and Pelz and completed in 1897. Behind its Italian Renaissance facades are two open courtyards formed by its modified Greek Cross plan, at the center of which is the great, octagonal, 100-foot-diameter reading room. One of Washington's most formidable spaces, it has been characterized by the AIA's Washington architectural guide as a space where "the opening of a book becomes a noble rite."

*The Corcoran Gallery and School of Art, designed by Ernest Flagg, built in 1897 diagonally across the street from the Old Executive Office Building. Modest in scale by comparison, it contains a pair of classically detailed, two-story, sky-lit atrium spaces around which art galleries were placed. Glass block panels set in the floor of the atrium spaces transmitted light to basement art studios.

*The Romanesque, 1899 Old Post Office building on Pennsylvania Avenue, designed by W. J. Edbrooke, architect for the Treasury. It contains a monumental atrium similar in spirit and intent to the Pension Building space. Ringed by offices filled with postal workers, it introduced light, air and a sense of commonality and grandeur into an otherwise thick and massive building destined for the usually tedious and banal tasks of sorting and distributing daily mail.

*The Pan-American Union Building at 17th and Constitution Avenue NW, south of the Corcoran, designed by Albert Kelsey and Paul Cret in 1910. Its intimate interior patio, suffused with light from above, contains a garden with tropical plants and serves as a unifying courtyard space through which visitors and employes move regularly.

In the 1920s and '30s, many massive federal office buildings were erected with courtyards carved out of them. Most notable are those of the Federal Triangle. These huge edifices were rendered humane and reasonably fit for occupancy only through the creation of interior voids open to the sky.

There are 20 such courtyards in five of the Federal Triangle's buildings. The mammoth 1,000-foot-long, 300-foot-wide Department of Commerce has six separate courtyards. Probably few people know of their existence, including perhaps government employes working in the building. Only two of Commerce's courtyards find any expression on the building's exterior facade. They provide parking and through access (for departmental visitors and employes) between 14th and 15th streets, while the other four courts contain gardens and mechanical equipment.

The Post Office Department contains asymmetric pentagonal courts with two sides curved to reflect the curvature of exterior facades forming the semicircular spaces on the east and west sides. The Justice Department building envelops courts of radically different sizes. Its major courtyard, the Triangle's largest, dominates three smaller ones at the southeast, southwest and northwest corners of the trapezoidally shaped building. All were intended to provide ventilation, light and views for the hundreds of surrounding offices.

Not to be outdone by Commerce, the War Department in 1940 completed the Pentagon, a five-story behemoth comprising five concentric layers of offices threaded together by nearly 18 miles of double-loaded corridor. The innermost of the five layers encompasses a gigantic grass-covered courtyard dotted by trees. Between each office layer are long, narrow slots of space, sliver-like courts offering views between opposing wings' parallel window walls a few feet away from each other.

But after World War II, architects and developers began to explore the covered-courtyard possibility anew. Some thought that the environmentally controlled and controlling atrium concept might be applicable to ordinary, everyday architecture, not just monumental civic buildings. Further, safety problems, which had prompted building codes to outlaw enclosed, multistoried atrium spaces, seemed susceptible to resolution through more sophisticated methods of ventilation, smoke extraction and fire control.

Also, well-known historical, clearly mercantile precedents existed in Europe. Buildings such as the 1867 Milan Galleria, a glass-vaulted, six-story shopping arcade imbedded in the city's fabric, appeared to thrive as viable commercial enterprises. Its architectural qualities not only were well known, but also attracted customers in great numbers year after year.

Even Frank Lloyd Wright designed atrium building prototypes. His 1903 Larkin Office Building in Buffalo, the 1936 Johnson's Wax headquarters building in Racine, Wis., and the 1959 Guggenheim Museum in New York all were structures that, like the Old Pension Building, were centered on unifying, vertically soaring, skylighted volumes.

Richard Saxon, author of "Atrium Buildings," characterizes Wright's work as transitional between two "atrium periods." The first, having its roots in the 19th century, ended about World War I, and the second started only about 20 years ago. He attributes this half-century lull partly to the then-prevailing modernist design fascination with skyscrapers and free-standing buildings, coupled with popular rejection of the "lightwell" image often associated negatively with tenement buildings.

Along with technological advances and building-code reform, two latter-day real estate phenomena in America provided the compelling impetus for revival of the atrium concept. First was the advent and proliferation of the regional, enclosed shopping mall that swept suburbia. Architect Victor Gruen, perhaps more than anyone else, can be credited with initially advocating and vigorously promoting this "new" design idea in the 1950s. He was joined with equal enthusiasm by pioneering shopping center developers such as Jim Rouse.

Then in the mid-1960s, another architect pushed "an idea whose time had come." John Portman designed the Regency Hyatt Hotel, built in Atlanta in 1967, although not the first of his now-famous atrium buildings. A developer as well as a designer, Portman demonstrated convincingly the economic and technical feasibility of using a glass-roofed, grandiose, people- and plant-filled atrium in a commercial edifice devoted to making a profit.

Most important, it was a smash hit on the general public's architectural pop chart with its visual drama, its wall-crawling transparent elevators, and its nearly-round-the-clock bar service. The die was cast, the second atrium period had begun, and Washington was to be a willing participant.

NEXT: The last 20 years.