Two-year-old Adrian Rivera's fascination with trains began with a video that his dad, Rafael, says the tot "watches for eight hours straight."

Yesterday, Adrian, of Fairfax City, was in railroad heaven along with thousands of other children and adults who swarmed into the Capitol Limited 2004 Model Train Convention at the Dulles Expo Center in Chantilly.

"Uh oh! Uh oh!" Adrian said, watching from atop his father's shoulders as two trains headed toward each other on different tracks. Rafael Rivera, 57, was videotaping the model trains to make his own tape for his son. The homemade video, which the father plans to splice together from four hours of convention footage, "should last [Adrian] a year," Rivera said.

More than 3,000 model train enthusiasts and others arrived within the first hour the convention was open to the public, indicating unusually high interest, convention officials said.

They came to see an almost half-mile-long electrified railroad track on which more than 50 tiny trains navigated the space of a football field. Sponsors estimated that it takes two hours to stroll around the perimeter of what they said was the world's largest train layout. The convention continues today, from 10 a.m. to 4 p.m.

Dozens of parents such as Rivera placed small children on their shoulders to give the squealing, clapping kids a giant's-eye view of a world 1/160th the size of their own. Miniature figures of people living around the railroad tracks -- hanging laundry outside or walking with their children -- were shorter than the diameter of a penny.

"This is definitely a family affair," said organizer Brian Brendel, 44, a Fairfax County fire captain who attended with his son and wife. "It's not just a bunch of [men] playing with their toys."

Called N scale, the model trains were introduced in the 1960s and run on tracks 9 millimeters wide. They are one-fourth the size of Lionel model trains, which boomed in popularity in the 1950s and '60s after plastics became more widely available following World War II.

Exhibitors came from 31 states and Japan, Australia, New Zealand, Germany and Switzerland. They are the ones who join their rail pieces into an electrified jigsaw puzzle of imaginary scenes and replicas of existing locations.

"This is the only [model train event] that lets you connect with this many people at one time and have everything work," said Dan Sullivan, 49, of Jackson, Mich., west of Ann Arbor. His portion of the train layout had 16 tracks, four of which were operating, and depicted a "generic" freight yard.

"We tried to make it look like Michigan -- very Midwest and nothing fancy," he said.

Other exhibitors created fantastic scenes, including one of New York City in which King Kong scowled atop a skyscraper at airplanes that circled him, suspended from thin wires.

A cow and wooden debris spun around in a tornado that roared across devastated farmland in Suzi Blust's portion of the train track. The 53-year-old Missouri resident wrapped cotton batting over chicken wire to create a giant, menacing cloud and used strobe lights to mimic lightning. A tape recording of a storm and tornado sirens that had wailed outside St. Louis surprised many viewers.

Fumiaki Oshida, a 65-year-old clockmaker from Tokyo, has loved model trains for more than 30 years. Over three years, in anticipation of the Chantilly convention, he built a model of a suspension bridge that joins Shikoku and Honshu islands. It is Oshida's first visit to the United States.

"His dream was to come to the U.S. to connect to the U.S. model trains," said another Japanese exhibitor, Nobuyuki Mizunuma, who interpreted.

Other attendees satisfied their dreams by visiting the other half of the convention hall, which was filled with vendors selling train paraphernalia.

Brendel's 9-year-old son, Jake, has his heart set on mini replicas of Amtrak passenger trains; each sleeper train is about the size of "a Milky Way and a half," Brendel said.

At Jake's home, his father's train set takes up a 15-foot-by-12-foot space in the family room.

"We had to cut a hole in the wall in the laundry room and into the bathroom" to accommodate the trains, Jake said. "When you're in the bathroom, you can see the train go by."

The trains at the convention are 1/160th the size of the real thing.Catherine Crossett, 6, and her brother James, 13, of Centreville look at a display at the model train convention in Chantilly.