By ROBERT SHAROFF
William Zharen for The New York Times

Construction of the Aqua Tower is expected to begin this fall.
MILLENNIUM PARK, the $475 million modernist playground that opened at the edge of Lake Michigan here two years ago, has quickly become one of the city's leading tourist attractions. What is less known, however, is that the 24.6-acre park ? which features a stunning stainless steel band shell and pedestrian bridge designed by the architect Frank Gehry, along with art and gardens by a galaxy of international figures ? has had a transforming effect on the surrounding neighborhood.

In the late 1990's, the area, known as the East Loop or South Michigan Avenue, was a fairly sleepy retail and office district. In the last five years, however, it has emerged as one of the city's hottest residential neighborhoods with more than a dozen projects rising within blocks of the park.

According to a study commissioned by the city in 2005, the park is responsible for about $1.4 billion in residential development and for increasing residential real estate values in the area by $100 a square foot.

"The East Loop has become an incredibly vibrant asset for the city," said Lori T. Healey, the city's planning commissioner. What has been created there is a mixed-use, round-the-clock neighborhood that includes office, residential, entertainment and open space. "It's a great symbiotic relationship."

Real estate executives agree. "You've got the park, the harbor, Navy Pier, the museums and other cultural attractions and easy access to expressways and public transportation," said James Kinney, president of Rubloff Residential Properties, a real estate brokerage firm. "It's a pretty unbeatable combination."

Others believe the success of the park is contributing to a shift in housing patterns across the city. "The epicenter of urban living in downtown Chicago has been progressively moving south for the last 5 to 10 years," said Thomas O. Weeks, president of the LR Development Company, developer of 340 on the Park, a high-rise condominium building under construction across Randolph Street from the park. "I think there will come a time when Millennium and Grant Parks will define residential living in Chicago much like Central Park does in New York," he said.

(Millennium Park is adjacent to Grant Park, a much larger park to the south that is part of a chain of parks created more than a century ago along the city's lakefront.)

The most successful project to date is probably the Heritage at Millennium Park, a 57-story condominium tower completed 18 months ago on nearby Wabash Avenue with unobstructed views of the park and lake. The building, which has 357 units, sold out well before it was finished at prices ranging from $245,000 for an 800-square-foot studio to $3.5 million for a 5,060-square-foot penthouse.

"The park was the catalyst for realizing this could be a residential neighborhood," said Richard Hanson, a principal with Mesa Development, the project's developer. "I don't think the building would have been viable without it."

In July, Mr. Hanson will break ground on a second tower, called the Legacy, on a site two blocks south of the Heritage. Just over 60 percent of the 355 units have already been sold at prices ranging from $300,000 for an 875-square-foot one-bedroom to $7.8 million for a 9,301-square-foot penthouse.

The buyers for both projects, he said, are mainly "young professionals, empty-nesters and people who are leaving 4,000-square-foot homes in the suburbs and need larger units."

Susan Grosch and her husband, Tony, who bought a two-bedroom unit at the Heritage, are in the second category. Mrs. Grosch is a retired public school teacher while her husband is a lecturer in the English department at the University of Illinois at Chicago. The couple formerly lived in a lakefront neighborhood several miles north of the Loop.

"My husband had wanted to move downtown for many years and periodically would ask me what I thought of this or that location," she said. "I was never very interested until one morning he said, 'How about Millennium Park?' And I said, 'Now, that sounds interesting.' "

The draw is the neighborhood. "We love the convenience, especially being able to walk to so many of the cultural venues, where in the past we've either had to drive or take a bus," she said.

The project that has caused the most stir architecturally is the Aqua Tower, an 80-story high-rise by the architect Jeanne Gang. It will consist of a 215-room hotel and 476 rental apartments on the lower floors and 263 condos on top. The building ? which is at least 50 percent sold at prices ranging from $342,000 for an 674-square-foot studio to $2 million for a 3,100-square-foot penthouse ? is to begin construction this fall and to be finished in 2009.

The building has a sensuous rippling facade created through the use of irregularly shaped concrete floor slabs. Ms. Gang, a prot?? of the Dutch architect Rem Koolhaas, said the inspiration was striated limestone outcroppings that are a common topographic feature of the Great Lakes region.