The results could have been worse. The enormous steel canopy of Norman Foster’s opera house has a pleasant, almost affectionate relationship with the low Cubist forms of Brad Cloepfil’s performing and visual arts high school next door. Rem Koolhaas’s and Joshua Prince-Ramus’s cool and somber aluminum-clad theater tower across the street, by contrast, is an aggressive rejection of the visual noise that many have come to expect when a star architect is hired to design a cultural building. What’s more, the new buildings sit comfortably alongside older structures like I.M. Pei’s concert hall and Edward Larrabee Barnes’s art museum, extending the conversation across generations as well as contrasting architectural philosophies.

What the planners could not easily overcome, however, was the scale of destruction, and the resistance many felt toward breaking down old barriers. Nearly 30 years after the plan was unveiled, most of the commercial lots remain empty. And the divisions that continue to separate this enclave of high culture from the nearby communities remain deep.

No project better illustrates these tensions than Los Angeles’ downtown arts district, which was conceived in the 1950s as an elite cultural citadel fortified against the surrounding Latino neighborhoods. To build it, civic leaders approved the bulldozing of a sprawling, decayed residential neighborhood of two-story Victorian houses. The Music Center, completed in the 1960s, was isolated on a concrete base in the style of Lincoln Center. The Harbor Freeway, partly built around the same time, cut the site off from the city to the west. The area’s isolation was further reinforced in the 1980s with the construction of sterile corporate towers and plazas, which formed a barrier against the Latino communities that occupied the old historic corridor nearby.

Walt Disney Concert Hall, completed six years ago, was the first sincere effort to reverse this trend. Frank Gehry went to great pains to fuse his building with the city around it. The ribbons of shiny stainless steel that envelop the structure lift up seductively along Grand Avenue to draw passersby into the lobby. Just above, the facade swells out to echo the curves of the Music Center’s Dorothy Chandler Pavilion next door, a gesture that gives the old structure sudden, unexpected grace.

But if Mr. Gehry’s creation has brought instant vitality to the street, it also demonstrates architecture’s limits as an agent for social healing. Even as the building was rising, Mr. Gehry and a choir of other voices were lobbying hard to break down the physical barriers that isolated the avenue from the rest of downtown. Many of the solutions were obvious. Mr. Gehry produced an elegant design to bring the Music Center’s plaza down to the level of the avenue. Civic leaders envisioned a park that would extend east from the base of the Music Center down to City Hall, linking the arts district to downtown’s civic core. So far these proposals have come to naught, and just as in Dallas, vast lots bulldozed decades ago remain undeveloped.

The failures in Dallas and Los Angeles, in the end, have less to do with too much creative freedom, the quality of the buildings and the master plan, or even the basic concept of an arts district, than with scale and context. They reflect the long battle between those who want to tear down old barriers and those who simply want to replace them with new ones. Solving that conflict will be left to a future epoch.