The ride begins here, where roofline meets skyline and pepper-colored concrete spans teasingly below.

Atop the 10-foot-tall building, Joel Dempsey poises next to a unicycle leaning against the brick wall.

One look at the 10-foot-tall unicycle and the reasonable would hesitiate, finally retreating. But Dempsey slips eagerly onto the slim seat.

Balance is the key here. Eyes focus forward, arms extend outward and the feet, the feet always move. One slip, and unicycle, body and concrete would blend into a tangled heap.

Without a hitch, Dempsey pushes off the building's edge, his 6-1 frame towering over the basketball goals around the school yard. First one trick, then another -- fancy spins, figure eights -- backward and forward, never stopping.

Three basketballs juggle from hand to hand. Then, a wind-sucking noise rushes overhead: Three fire-torched clubs dance in front of Dempsey's chest, cutting the air.

Dempsey is a unicyclist, a national champion.

The ruddy-faced Fairfax County youth also is a football player, a baseball player, a trapeze artist, a first-year high school student, son of a lawyer and a 14-year-old boy from the suburbs who wants to join the circus.

"Some people think I'm crazy or joking when I tell them I want to join the circus, but I'm not," Dempsey says reticently. "I don't like the suburbs and I don't want to work in a business and sit behind a desk all the day.

"I feel relaxed and free when I'm performing. I love performing and hearing the applause -- it makes me do everything better."

Dempsey's road from pedestrian mobility to one-wheeled gliding to the national trick unicycle championship this summer in Kokomo, Ind. began three and a half years ago when he was a student at Oakview Elementary School.

There, under the guidance of physical education coach Jim Moyer, he quickly advanced from a three-foot unicycle to the standard 10-foot circus model.

"What makes Joel good is that he is just so strong. He manhandles the unicycle, forcing it to do what he wants to do," says Moyer, who still coaches Dempsey a couple of hours nearly every day.

"It (unicycling) is his first and only love," says Joel's mother, Cathy Dempsey. "I thought when he went to high school other sports might take its place. But they haven't. He plays the other sports, but he always comes home, eats dinner and then goes up to the (Oakview) gym to practice."

Inside that gym is the reason a nice middle-class kid want to leave the comforts of a nice suburban home and take his chances on the long-shot of becoming a circus star -- and the reason his parents encourage him to follow that dream to the Big Tent.

The key is Jim Moyer and his 13-year-old after-school circus program.

"He's one of those rare birds you hear about," says Jack Dempsey as he describes his son's coach. "You look around and see what could be done in any other school. Just because of an accident of moving, our kids have been exposed to something they really love."

Three of the five Dempsey children are in Moyer's program, and all three want to join the circus.

The circus seems to have arrived in the Oakview gym. German gym wheels, high-wire ropes, vividly painted ladders, stilts, unicycles, a trapeze and a trampoline are only some of the circus apparatus set up in the cluttered gym.

Young girls wearing leotards plummet through the air, somersaulting and diving, doing something those versed in circus lingo call a "quartet adagio."

Moyer says he began the program -- which includes more than 70 school children and put on as many shows last year -- as an alternative to competitive team sports.

"There's no pressure here," Moyer says."A kid doesn't have to come to practice if he has something else to do. I have always felt that the control of the body and poise learned from circus gymnastics was important and invaluable. The compeitition is unimportant."

Moyer may be teaching that poise and control to the Dempseys for some time to come. One day recently, as Joel and his parents were leaving the gym, the youngest Dempsey, 2-year-old Jennifer, squealed from the corner of the room. There, reaching arduously for the balance beam, her pudgy toes arched above the floor, she motioned for help.

Hoisted up by her father, Jennifer swung contentedly back and forth, the circus gleam in her eye.