John C. Portman Jr. sits among the buildings of the Peachtree Center in Atlanta. (Michael Portman/Portman Image Archive)

John C. Portman Jr., an architect whose hotel, shopping and office complexes tower over the major cities of the world, and whose cavernous atriums, replete with waterfalls, fountains, ivy and spiral staircases, redefined the look of the modern hotel, died Dec. 29 in Atlanta. He was 93.

His death was announced in a statement provided by the Edelman communications firm. No cause was cited.

Mr. Portman was perhaps most identified with Atlanta, where his architecture firm, John Portman & Associates, was headquartered, and where he burst to the fore in 1967 with the 22-story Hyatt Regency, which popularized what would become his signature atrium concept.

“Before John Portman started designing them, hotels were not glass cylinders sitting on concrete bases,” read a 1986 New York Times editorial. “Neither did their lobbies sport lakes and open upward into atriums; nor did glass elevators scuttle up and down like transparent beetles.”

To an arriving visitor, the effect of a Portman atrium was astonishing. Former Atlanta mayor Andrew Young once remarked that “everybody became a country bumpkin when they walked into the Hyatt.”

Mr. Portman’s Renaissance Center towers over Detroit. (Michael Portman/Portman Image Archive)

Mr. Portman also was the principal architect and developer of Atlanta’s Peachtree Center, a 14-block district that features office space, shopping and dining, with Venetian-inspired pedestrian bridges connecting one structure to another.

But he helped shape cities around the world with designs such as the Marriott Marquis in New York’s Times Square, the Renaissance Center in Detroit, the Embarcadero Center in San Francisco and massive complexes across Singapore, China, South Korea, India and beyond.

His career coincided with the decline of downtown neighborhoods as the locus of American social life. Through his designs, he sought to draw people back to the city center.

“Architecture is a social art, not a private art,” he told Forbes magazine in 1982, explaining the overriding philosophy of his work. “A building sits out on the corner. So the most important thing is creating an environment that all of the people respond to, not just the highly educated aesthete but the man on the street.”

To their critics, Mr. Portman’s buildings succeeded in attracting shoppers, tourists and businesses travelers but did little to reinvigorate city life. His complexes, like self-sustaining commercial ecosystems, were very nearly cities unto themselves.

New York Times architecture critic Paul Goldberger once called Mr. Portman “a kind of P.T. Barnum of the hotel business,” referring to the circus showman, and described the $400 million Marriott Marquis and its 48-story atrium as the Edsel of architecture — “awkward, gangling and out of touch.”

Yet in their spaciousness, Mr. Portman’s buildings had an undeniable appeal. His atrium design was replicated in hotels across the world — suggesting that perhaps he had found a solution to some gnawing and widespread problem.

“What do urban areas need the most? Space,” Mr. Portman once remarked. “Sidewalks and congested areas have a lot of anxiety, and I wanted to create a release from that anxiety.”

John Calvin Portman Jr. was born Dec. 4, 1924, in Walhalla, S.C., where his mother, a beautician, was traveling at the time. His father worked for the government, and Mr. Portman grew up in Atlanta.

A mechanical drawing class in junior high school was his first exposure to architecture. He persuaded his high school to allow him to study architecture at a vocational school, according to Forbes.

Mr. Portman attended the U.S. Naval Academy before receiving a bachelor’s degree in architecture from Georgia Tech in 1950.

Beginning early in his career, he pursued the dual track, unusual among architects, of development as well as design. In the 1970s, he teamed with the National Press Club in Washington to propose a plan for an expansive commercial complex that would have resulted in the destruction of the National Theatre. The plan, forcefully opposed by critics including actress Carol Channing, was ultimately rejected.

After he became widely known for his projects in the United States, Mr. Portman’s international work helped pull him out of a financial crisis in the 1990s.

Survivors include his wife of 73 years, the former Joan “Jan” Newton; five children, Michael Portman, John C. “Jack” Portman III, Jeffrey Portman, Jana Portman Simmons and Jarel Portman; three sisters; 19 grandchildren; and five great-grandchildren. His son Jae Portman died in 2003.

Today Mr. Portman’s atrium design greets travelers in hotels around the world. It is so common as to have perhaps become a “cliche,” Mr. Portman conceded. “The thing about architecture is that once you leave the site and you go on,” he told the Times in 2006, “you’re just in the hands of destiny.”