''A city is a place where a small boy when he walks through it may see something that will tell him what he wants to do with his whole life,'' architect Louis Kahn once observed.
And so the city has spoken to and inspired architects through all ages.
Louis Sullivan, credited with the invention of the skyscraper, was already smitten with the city's buildings when an elegant passerby on its streets moved him still more. He wished ''to know who and what kind of man was behind the dignity,'' he wrote later.
''Who was the high-hatted figure stepping into a carriage?'' he asked a worker on the site.
''Why he's the architect of this building,'' a workman said. And a star was born.
Convention has it that architects are made otherwise - by their passion for erector sets, their Lincoln-log adolescence, their tinker-toy childhood. Such are the blocks that build our builders, legend claims.
Historians say playing with the Froebel block helped make Frank Lloyd Wright; feminists worry that no play with blocks - building-block deprivation - has denied their daughters access to the field.
If that is the case, then the Lego Block, the 50-year-old construction toy, may have inspired a new generation to take their talents for meshing interlocking parts into a modern design a step further.
Now in their fifth year, the so-called road shows of the Danish design company may be the most omnipresent architecture show in the country, taking a wide variety of forms - from Washington's Capitol to the Eiffel Tower. Now in Dayton's department store in Minneapolis and the Hallmark mall in St. Louis, the exhibition awes onlookers with its capacity for building architectural mountains out of Lego molehills.
The Road Show No. 5, witnessed recently, has its delights. The chest-high US Capitol - stairs swelling from the floor of the department store exhibit area, the details executed in tiny plastic parts - is in the Guinness Book of World Records mode. Visitors are invited to compete in counting the number of Legos employed; youngsters sit at tables and try their hand at copying the models, or creating their own.
Director Bill Higgins of the Lego Company credits the blocks (''the leading construction toy'') with breeding a new generation of architects. His own model builder, Dave Scerundolo, grew up with Legos, and Higgins has great visions of Lego stackers growing up to create sky-high buildings.
''There isn't a place that the sun sets that a kid isn't playing with Lego,'' Higgins says.
The road to a profession is not a straight path, however, and the start of the school year should suggest that there is more than one route to learning design.
Whether the architectural role model - perhaps Daddy Brady in The Brady Bunch - or Vance Packard, placing the architectural profession in high esteem, will inspire the next generation of architects is unknown, but many architects now living arrived at their calling in circular fashion, indeed.
For instance, Denise Scott-Brown of the firm of Venturi, Rauch & Scott-Brown, simply thought that architecture was ''women's work.'' Her mother studied the subject and practiced in Zimbabwe. The young Denise followed her role - drawing, working with her hands, and, finally, attending architecture school, where she discovered, to her great surprise, that her classmates were mostly men.
Her husband, Robert Venturi, growing up in America, the son of Italian parents, thought architecture was a field of everyday cultural concern, like the proverbial opera, she says.
His fruit-merchant father had a splendid design for his store in the '20s - and books ''with beautiful pictures of Italian architecture'' filled their home, she says.
A reverence for a profession sometimes determines the final choice. Frances Steloff, the famous bookseller, who figured in a recent book charting professional passions (''Particular Passions''), wrote of a father who ''if he ever dropped one of his books on the floor, he picked it up and kissed it.''
Unfortunately for architecture, buildings are not objects of that kind of reverence. Many designers came to architecture by default. Bill Grover of Moore Grover Harper wanted to be an inventor, trained for the field, but found more invention possible in design.
Kevin Roche, who won this year's prestigious Pritzger Prize, came to architecture by an even greater default: ''I was an absolutely hopeless student, '' he says. ''(Architecture) was one of the few things I could do.'' Though Roche's parents thought architecture was a ''mildly indecent thing'' for a boy growing up in a small Irish town to do, Roche may have had a subliminal visual education in the handsome, formal town planning of his native Mitchelstown, he says.
Similarly, critics have suggested that Frank Lloyd Wright's changing visual surroundings during his roaming youth were - along with the blocks - a source of his sense for altering the built environment.
Paul Rudolph, the son of a minister, has cited his peripatetic youth, moving from parish to parish, plus his mother's touch with flowers on the table, as the origin of his architectural strivings.
Proximity to great architecture or architects like Wright clearly doesn't hurt. The great Viennese architect Otto Wagner claimed that the day his successful architect grandfather took him for a ride in a splendid carriage his career started:
''Impressed by such opulence, the boy decided there and then to enter this lucrative profession,'' Richard J. Neutra, the famous modernist, observed.
Richard Haas, whose murals that mimic buildings have become as prevalent as many types of buildings, came by his architecture through the same kind of aura. Growing up a mile south of Frank Lloyd Wright's home, Taliesin, in Spring Green, Wis., Midwesterner Haas had a sense of a glamorous mystique. He remembered well when Wright ''in his flat hat, can, and cape stepped out of a rust-colored Lincoln Continental with an oval rear window; the other members of the Taliesin Fellowship parked miniature Austins of the same color nearby.'' Their world of mystery wafted toward him.
And in the end, that mystery, more than any building blocks, may account for the coming to and capability of those in architecture.