Rem Koolhaas has been causing trouble in the world of architecture since his student days in London in the early 1970s. Architects want to build, and as they age most are willing to tone down their work if it will land them a juicy commission. But Koolhaas, 67, has remained a first-rate provocateur who, even in our conservative times, just can’t seem to behave. His China Central Television headquarters building, completed this past May, was described by some critics as a cynical work of propaganda and by others (including this one) as a masterpiece. Earlier projects have alternately awed and infuriated those who have followed his career, including a proposal to transform part of the Museum of Modern Art into a kind of ministry of self-promotion called MoMA Inc. (rejected) and an addition to the Whitney Museum of American Art that would loom over the existing landmark building like a cat pawing a ball of yarn (dropped).

Koolhaas’ habit of shaking up established conventions has made him one of the most influential architects of his generation. A disproportionate number of the profession’s rising stars, including Winy Maas of the Dutch firm MVRDV and Bjarke Ingels of the Copenhagen-based BIG, did stints in his office. Architects dig through his books looking for ideas; students all over the world emulate him. The attraction lies, in part, in his ability to keep us off balance. Unlike other architects of his stature, such as Frank Gehry or Zaha Hadid, who have continued to refine their singular aesthetic visions over long careers, Koolhaas works like a conceptual artist—able to draw on a seemingly endless reservoir of ideas.

Yet Koolhaas’ most provocative—and in many ways least understood—contribution to the cultural landscape is as an urban thinker. Not since Le Corbusier mapped his vision of the Modernist city in the 1920s and ’30s has an architect covered so much territory. Koolhaas has traveled hundreds of thousands of miles in search of commissions. Along the way, he has written half a dozen books on the evolution of the contemporary metropolis and designed master plans for, among other places, suburban Paris, the Libyan desert and Hong Kong.

His restless nature has led him to unexpected subjects. In an exhibition first shown at the 2010 Venice Biennale, he sought to demonstrate how preservation has contributed to a kind of collective amnesia by transforming historic districts into stage sets for tourists while airbrushing out buildings that represent more uncomfortable chapters in our past. He is now writing a book on the countryside, a subject that has been largely ignored by generations of planners who regarded the city as the crucible of modern life. If Koolhaas’ urban work has a unifying theme, it is his vision of the metropolis as a world of extremes—open to every kind of human experience. “Change tends to fill people with this incredible fear,” Koolhaas said as we sat in his Rotterdam office flipping through an early mock-up of his latest book. “We are surrounded by crisismongers who see the city in terms of decline. I kind of automatically embrace the change. Then I try to find ways in which change can be mobilized to strengthen the original identity. It’s a weird combination of having faith and having no faith.”

Tall and fit in a tapered dark blue shirt, with inquisitive eyes, Koolhaas often seems impatient when talking about his work, and he frequently gets up to search for a book or an image. His firm, OMA, for the Office for Metropolitan Architecture, employs 325 architects, with branches in Hong Kong and New York, but Koolhaas likes the comparative isolation of Rotterdam, a tough port city. Housed in a brawny concrete and glass building, his office is arranged in big, open floors, like a factory. On the Sunday morning we met, a dozen or so architects sat silently at long worktables in front of their computers. Models of various projects, some so big you could step inside them, were scattered everywhere.

Unlike most architects of his stature, Koolhaas participates in many competitions. The process allows for creative freedom, since a client isn’t hovering, but it’s also risky. The firm invests an enormous amount of time and money in projects that will never get built. To Koolhaas, this seems to be an acceptable trade-off. “I’ve absolutely never thought about money or economic issues,” Koolhaas said. “But as an architect I think this is a strength. It allows me to be irresponsible and to invest in my work.”

Koolhaas’ first test of his urban theories came in the mid-1990s, when he won a commission to design a sprawling development on the outskirts of Lille, a rundown industrial city in northern France whose economy was once based on mining and textiles. Linked to a new high-speed rail line, the development, called Euralille, included a shopping mall, conference and exhibition center, and office towers surrounded by a tangle of freeways and train tracks. Seeking to give it the richness and complexity of an older city, Koolhaas envisioned a pileup of urban attractions. A concrete chasm, crisscrossed by bridges and escalators, would connect an underground parking garage to a new train station; a row of mismatched office towers would straddle the station’s tracks. For added variety, celebrated architects were brought in to design the various buildings; Koolhaas designed the convention hall.

More than a decade after its completion, Koolhaas and I meet in front of Congrexpo, the convention hall, to see how the development looks today. An elliptical shell, the colossal building is sliced into three parts, with a 6,000-seat concert hall at one end, a conference hall with three auditoriums in the middle and a 215,000-square-foot exhibition space at the other.

On this Saturday afternoon the building is empty. Koolhaas had to notify city officials to get access, and they’re waiting for us inside. When Koolhaas was hired to design the building, he was still perceived as a rising talent; today he is a major cultural figure—a Pritzker Prize-winning architect who is regularly profiled in magazines and on television—and the officials are clearly excited to meet him. His presence seems to bring cultural validity to their provincial city.

Koolhaas is polite but seems eager to escape. After a cup of coffee, we excuse ourselves and begin to navigate our way through the hall’s cavernous rooms. Occasionally, he stops to draw my attention to an architectural feature: the moody ambience, for instance, of an auditorium clad in plywood and synthetic leather. When we reach the main concert space, a raw concrete shell, we stand there for a long while. Koolhaas sometimes seems to be a reluctant architect—someone who is unconcerned with conventional ideas of beauty—but he is a master of the craft, and I can’t help marveling at the intimacy of the space. The room is perfectly proportioned, so that even sitting at the back of the upper balcony you feel as though you were pressing up against the stage.