It erupted as a primal scream from a frazzled-looking conventioneer leaning against a wall, hair askew, punctuated by a complaint repeated by others in corridors and grand spaces: “Get me out of here!” Not everyone felt it; many, if not most, reveled in the mix. Still, some visitors to the rousingly successful AIA National Convention, which attracted a record number (24,500) to its positive energy, experienced a type of sensory overload and psychological distress. Their discomfiture bears scrutiny, since the source of their collective angst lies embedded in architecture.

The problem, in a word, is Big. It makes some of us, like the distressed visitor, lose our emotional cool. The occasional human reaction to excessively fulsome crowds and sizable spaces has a big name for a real condition—agoraphobia. In its classic sense, the term refers to the fear of open spaces. Related to claustrophobia, it breeds in gigantic enclosures, and includes phobias centered on crowds, shops, and public places; psychologists describe one operable variant as the fear of shopping malls. Fueled by large milling crowds, it can produce a kind of nameless panic, exacerbated by hermetic environments such as the typical humongous Las Vegas casino/hotel/convention complex, where visible exits to air and sunlight are remote, few, and hard to find.

You may have experienced twinges of its effects in high-rise New York, or like Bill Murray in the movie Lost in Translation, who was hit with a heavy case of ennui awakening in a hotel tower far above Tokyo. Dislocated and out of sorts, he was literally, hilariously removed from reality and mired in an existential dilemma. He, and a few conventioneers in Nevada, suffered distress, if not full-blown agoraphobia. Sound familiar?

What are the architectural determinants of this mini-paranoia? A primary cause is scale. Despite the American penchant for the super-sized, not all vastness is benevolent: Gigantism contains traces of bombast and overt manipulation mixed in with the fun. At mass gathering places, with few retreats for intimacy or personal space, we are literally being herded and told how to feel. In hotels with 5,000 rooms and tens of thousands of conventioneers, mega-corridors that extend for hundreds of yards, as high and wide as Mammoth Cave, even those that twist and turn seductively can prove oppressive rather than expansive, stifling human presence and producing dread mixed with awe. Skylights, if placed too high, will not necessarily alleviate the gloom, nor will atria, which can contribute their own oppressive weight.

To scale, add excessive sensory stimulation. In the typical Vegas public interior, we are bombarded with sound, from the ’60s-funky Muzak in the elevators to the accelerating ka-chink of the slots. The air reeks of smoke, or air freshener, or eucalyptus. Oxygen whooshes; lights blink and pop. In the desert, where temperatures can soar above 100 degrees Fahrenheit in May, conditioned environments have superseded the open-air strip, permitting a seamless transition from internalized plane to car to hotel room. You never need break a sweat.

We might dismiss Vegas as our beloved aberration, our own neon American Pie, except for the way it has come to crystallize certain distinctly American values. The strip has become the urban equivalent of a halftime show at the Super Bowl—big and universally embraced here, but what is it all about? Since the world seems bent on adopting heroic American consumerism, it looks to Las Vegas as much as to Main Street, U.S.A. The massively scaled cities of China and India, for example, hold the potential for the best of urban life as well as the worst excesses of contemporary material culture. Will their reinvented cities ape the big, broad stroke or the fine-grained? Will they prove life-enhancing or overwhelming? Like it or not, Vegas seems to hold sway in the collective imagination.

Meanwhile, the desert city continues to pack ’em in, attracting 38 million tourists per annum, 6,000 to 8,000 new residents per month, and billions in construction dollars. The most expensive project yet built there, the sophisticated new Wynn resort complex, completed in 2004, cost $2.7 billion. The phenomenon is growing: Plans are under way for the MGM Mirage’s Project CityCenter, which will exceed any previous construction on the Richter scale, a strip metropolis on 66 acres of prime caliche. Super-size me!

The 2005 convention was a hit. People loved the town. But Las Vegas also teaches us to ask which American dream we are helping to construct, at home and abroad, and whether it will provoke delight or panic. Before you draw another line, ask what is the scale? Where is the door? Let me out of here!