I thought I had seen it all. I have dodged low-hanging water pipes at the Radio Central building in Tokyo's Akihabara electronics district in search of vacuum tubes for a treasured old amplifier. I have wandered Canal Street in New York City looking for deals on DVDs. But I have never seen anything like this.

As I emerge from the subway station in Seoul, South Korea, I am overwhelmed. Not by the hustle and bustle of a sprawling Asian city, but by the sight of the building towering over me—and by the knowledge that the whole building is populated by electronics merchants.

I am standing in Seoul's Yongsan district, an entire section of the city devoted to the electronics industry. The electronics mall I am about to enter is but one of three. Still more buildings, packed with electronics stores, stretch for blocks down the adjacent streets. I have been told that Yongsan holds more than 5,000 electronics stores devoted to such specialties as audio and video, appliances, computers, and lighting. I cannot imagine how I will explore it all, but I know I will not be able to stop until my legs refuse to go further.

Luckily, I have been tipped off as to which building is the best for consumer electronics: Electroland, a seven-story behemoth larger than the Macy's store on 34th Street in Manhattan (which proudly proclaims itself "The World's Largest Department Store").

Electroland's first three floors carry more than a hundred stores devoted to mass-market electronics. The first two floors focus on cameras, camcorders, and MP3 players; the third gets more into home products, with countless TVs, DVD players, and home-theater-in-a box systems on display.

The fourth floor, though, is where it gets good. Here is where South Koreans shop for the finest in audio. The stores here are not the capacious home theater showrooms that have become common in the United States, however. Instead, each dealer resides in a space no larger than a typical tract-home living room. Each of these rooms is packed so tightly with audio gear that there is room only for the proprietor and one customer. The customer sits down in front of a selection of CDs, and asks to hear a particular component or pair of speakers. The proprietor then activates the desired components through a complex patch bay that recalls an old-fashioned telephone switchboard.

Because of the glass wall behind the listening chair and the multitude of other speakers resonating in symphony with the speaker being played, the sound pales in comparison with what one hears in any good American hi-fi shop. Americans normally associate this sort of demonstration with mass-market electronics superstores, but Electroland's fourth-floor rooms are stocked with the world's most exclusive audio products. I recognize such storied brands as Thiel, Krell, Wilson Audio, Mark Levinson, Revel, Linn, and JMlab. I also spot a few exotic, bizarre speakers whose names I am only fleetingly familiar with; these products are almost unknown in the United States but rather popular in Asia's strangely fetishistic high-end audio market. I also see antique vacuum-tube amplifiers that date from the 1950s, and even a couple of reel-to-reel tape decks.

Electroland's delights do not end here. An entire floor plus some is dedicated to video games. I encounter one store that sells nothing but video projectors, and another that specializes in racks and stands. Up top, on the seventh floor, I browse stores selling DVDs and CDs. Among the expected Hollywood blockbusters, Hong Kong martial-arts movies, and unfamiliar Asian musical artists, I find substantial racks of jazz and blues CDs. I walk out with a bulging bag of titles, including many I have never seen in the U.S.

On the way out, I take one escalator too many and end up in the basement—which also turns out to be a wonderland. Tiny stores hawking a broad variety of electronic components occupy the entire dingy space. I see dealers specializing in integrated circuits, others specializing in motors, even stores devoted entirely to capacitors. It's a geek's heaven, something that could not exist in the United States, where electronics manufacturing is now rare and becoming rarer every day. Comparing Electroland's basement to Fry's Electronics, the most popular destination for U.S. nuts-and-bolts electronics enthusiasts, is like comparing a Safeway to a 7-11.

Having now explored two electronics malls—earlier, I walked Space 9, a nine-story electronics mall—I take stock of my legs. Despite my regular hikes in the hills around Los Angeles, I realize that I simply don't have it in me to see all of Yongsan. I thus decide to ignore the district's third electronics mall, the computer-oriented Sunin Plaza, and instead begin perusing the long two-story buildings that extend into the surrounding streets.

I find the most interesting shops near Electroland; these specialize in tools, adapters, plugs, and other curios fascinating to anyone with a hands-on interest in electronics. Each little shop comprises pegboards full of tools—some familiar, some less so—and countless boxes of tiny electrical parts. My supply of Korean won begins to evaporate. I cannot resist a strange angled screwdriver, a usefully stubby adjustable crescent wrench, and an inexplicably appealing pair of electrician's scissors. My prize find: a stock of beautiful little anodized aluminum banana plugs, some red, some blue, all with rugged, gold-plated contacts that look as if they emerged from a jewelry artisan rather than a factory in China. I buy the whole box.

More wonders appear: a row of stores that sells nothing but cell phones, another group devoted to security systems, more selling only blank CDs and DVDs, and a few others focusing on wire and cable. I notice that most of the shops in this section have back doors; I walk through one and emerge in an alley filled with colorful flags and signs, stacks of electronic components, and appliances being manhandled by stockboys ... and across the alley, a whole new row of stores to explore. But my legs are spent.

Even so, as I head back to the subway I cannot resist checking out the DVD stores that dot my path. I find a few gems, including a Miles Davis concert DVD from the mid-1980s and another featuring Todd Rundgren's Utopia—both titles I did not know existed. To my surprise, I see nothing in these shops that looks counterfeit. And having explored the DVD markets of Shanghai and New York City's Chinatown, I am pretty good at spotting the fake stuff.

Fortunately, my return trip takes me past what seems to be the one business in Yongsan not devoted to electronics—a tentlike structure housing a grille, a refrigerator, and a few tables. I spend my last few won on a Diet Coke and Korea's version of a corn dog, and settle down to rest my feet and marvel at my new banana plugs.