As the rest of Japan nurses its hangover from the bubble years, Minoru Mori, the country's most powerful and influential building tycoon, is partying like it's 1989. Shrugging at one of the worst real estate environments in Japanese history and sniffing at predictions of more property woes to come, the 68-year-old president and CEO of Mori Building recently cut the ribbon on his company's grandest achievement to date—a $2.25 billion, 11.6-hectare mega-complex comprising apartments, shops, restaurants, cafés, movie theaters, a museum, a hotel, a major TV studio, an outdoor amphitheater and a sprinkling of parks all anchored by a surprisingly attractive, barrel-chested 54-story office tower (designed by New York City-based firm Kohn Pedersen Fox Associates) smack in the heart of Tokyo's bustling Roppongi district. Called Roppongi Hills, the complex constitutes Japan's most ambitious urban- renewal scheme since the postwar era. Seventeen years in the making, it is also Mori's boldest declaration yet in his one-man campaign to save Tokyo from itself.

What about Tokyo needs saving, you may ask? Ugh, says Mori with a grimace and a sigh from across a titanic pink and white stone conference table at his company's headquarters (recently relocated to ... where else?). Mori hardly knows where to begin. Tokyo, he declares, is losing the race to remain the undisputed capital of Asia, primarily because it is such a difficult, ugly and expensive place to live. Thanks to a half-century of what he calls misguided zoning and public-policy decisions (spurred, in part, by earthquake-fear mongering and a fetishistic promotion of suburban home ownership), Tokyo's urban centers are disjointed agglomerations of short, shoddy buildings that empty out and shut down every evening (except for a few nightlife neighborhoods) as workers hop overcrowded trains to their cramped homes in the city's never-ending exurban hinterlands. "Commuting three hours a day is a reality for many people," Mori says. "But that leaves no time for them to be with their family, shop, go to a museum, go to a show or do any of the things that really make life enjoyable. Tokyo residents' quality of life is terrible."

And therein lies the master builder's self-appointed mission: to improve Tokyo's quality of life by erecting compact, complete, integrated, high-rise cities within the larger, sprawling megalopolis—self-sufficient hubs where all of life's necessities and most urban pleasures are within a few minutes' walk.

All this might sound like the same old utopian vision of the "vertical city" that legendary modern architect Le Corbusier and his legions of followers frequently attempted (yet usually failed) to achieve throughout the 20th century. But Roppongi Hills improves on the old model by recognizing the virtues of carefully engineering the built environment to seem more organic and evolving than it actually is, in part by mixing the uses and purposes of various street-level spaces.